I convert OSM Scene Loader (change syntax) from ODN (here in forum)
that was also converted from original c++ code.

May be this will be useful for someone..

Alternatively here is an other port of the OSM Scene Loader:
MOGRE OSMSceneLoader 2

Code:

//Update: 02/Feb/2007
//Fixed a problem with the code to parse float numbers,
//the code was dependent of the culture and the decimal separator.

using System;
using System.Collections;
using System.Drawing;
using System.IO;
using System.Xml;
using System.Globalization;
using Mogre;

namespace MyApp
{
    public class OSMLoader
    {
        private XmlDocument xd;
        private SceneManager mSceneMgr;
        private RenderWindow mWindow;
        private NumberFormatInfo numberFormat = new NumberFormatInfo();

        private const int SCENE_SKYPLANE = 1;
        private const int SCENE_SKYDOME = 2;
        private const int SCENE_SKYBOX = 3;

        private Hashtable cameras, lights, entities;

        public Hashtable Cameras
        {
            get { return cameras; }
        }

        public Hashtable Lights
        {
            get { return lights; }
        }

        public Hashtable Entities
        {
            get { return entities; }
        }

        public SceneManager SceneMgr
        {
            get { return mSceneMgr; }
        }

        public event LoadedSceneObjectEventHandler OnCameraCreate;
        public event LoadedSceneObjectEventHandler OnNodeCreate;
        public event LoadedSceneObjectEventHandler OnLightCreate;
        public event LoadedSceneObjectEventHandler OnEntityCreate;

        public OSMLoader(SceneManager mgr, RenderWindow wnd)
        {
            numberFormat.CurrencyDecimalSeparator = ".";
            mSceneMgr = mgr;
            mWindow = wnd;
            cameras = new Hashtable();
            entities = new Hashtable();
            lights = new Hashtable();
        }

        public void Initialize(string xmlFile)
        {
            LogManager.Singleton.LogMessage(@"
**********************************************
**            OSM Scene Loader              **
**********************************************
");
            LogManager.Singleton.LogMessage("OSMLoader loading scene form file: " + xmlFile);
            if (!ResourceGroupManager.Singleton.ResourceExists(
               ResourceGroupManager.DEFAULT_RESOURCE_GROUP_NAME,
               xmlFile))
            {
                LogManager.Singleton.LogMessage("Not found file: " + xmlFile);
                throw new FileNotFoundException("Not found scene file.", xmlFile);
            }

            xd = new XmlDocument();
            try
            {
                DataStreamPtr dsp = ResourceGroupManager.Singleton.OpenResource(xmlFile);
                xd.LoadXml(dsp.AsString);
                dsp.Dispose();
            }
            catch (XmlException ex)
            {
                xd = null;
                LogManager.Singleton.LogMessage("Can't parse scene data, detail error message:\r\n" + ex.Message);
                throw ex;
            }
        }

        public bool CreateScene(SceneNode parent)
        {
            if (xd == null) return false;
            LogManager.Singleton.LogMessage("OSMLoader: Creating scene on '" +
               (parent == null ? "Root" : parent.Name) + "' node.");

            if (mSceneMgr == null)
            {
                if (xd.SelectSingleNode("/sceneManager") != null)
                    setSceneProperties(xd);
                else
                    mSceneMgr = Root.Singleton.CreateSceneManager(SceneType.ST_GENERIC);
            }

            if (parent == null)
                parent = mSceneMgr.RootSceneNode.CreateChildSceneNode();

            try
            {
                CreateEntities(xd.SelectNodes("/oe_scene/entities/entity"), parent);
            }
            catch
            {
            }
            try
            {
                CreateLights(xd.SelectNodes("/oe_scene/lights/light"), parent);
            }
            catch
            {
            }
            try
            {
                CreateCameras(xd.SelectNodes("/oe_scene/cameras/camera"), parent);
            }
            catch
            {
            }

            LogManager.Singleton.LogMessage(@"
********************************
** oSceneLoader: Scene loaded **
********************************
");
            return true;
        }

        // no use
        /*
              private void declareResources()
              {
                 if (xd == null) return;
                 try
                 {
                    XmlElement xe = (XmlElement) xd.SelectSingleNode("/entities");
                    if (xe != null)
                       foreach (XmlElement item in xe.ChildNodes)
                          ResourceGroupManager.Instance.declareResource(item.GetAttribute("filename"), "Mesh");
                 }
                 catch
                 {
                 } // i don't know why not process exception here in c++ source file.
              }
        */

        private ColourValue parseColor(string r, string g, string b)
        {
            ColourValue clr = new ColourValue();
            clr.r = float.Parse(r, numberFormat);
            clr.g = float.Parse(g, numberFormat);
            clr.b = float.Parse(b, numberFormat);

            return clr;
        }

        private void setSceneProperties(XmlDocument xd)
        {
            // Scene manager
            XmlElement sceneMgrElem = (XmlElement)xd.SelectSingleNode("sceneManager");
            /*
               ST_GENERIC = 1,
               ST_EXTERIOR_CLOSE = 2,
               ST_EXTERIOR_FAR = 4,
               ST_EXTERIOR_REAL_FAR = 8,
               ST_INTERIOR = 16
             */
            int type = int.Parse(sceneMgrElem.GetAttribute("type"));
            SceneType sceneType = (SceneType)type;
            mSceneMgr = Root.Singleton.CreateSceneManager(sceneType);

            string worldGeometry = sceneMgrElem.GetAttribute("worldGeometry");
            if (worldGeometry != null)
                mSceneMgr.SetWorldGeometry(worldGeometry);

            // Background Color
            XmlElement colorElem = (XmlElement)xd.SelectSingleNode("bkgcolor");
            if (colorElem != null && mWindow != null)
            {
                ColourValue color = parseColor(
                   colorElem.GetAttribute("r"),
                   colorElem.GetAttribute("g"),
                   colorElem.GetAttribute("b"));

                mWindow.GetViewport(0).BackgroundColour = color;
            }

            // Ambient light Color
            colorElem = (XmlElement)xd.SelectSingleNode("lightColor");
            if (colorElem != null)
            {
                ColourValue color = parseColor(
                   colorElem.GetAttribute("r"),
                   colorElem.GetAttribute("g"),
                   colorElem.GetAttribute("b"));
                mSceneMgr.AmbientLight = color;
            }

            // Scene shadows
            XmlElement shadowsElem = (XmlElement)xd.SelectSingleNode("shadowTechnique");
            if (shadowsElem != null)
            {
                type = int.Parse(shadowsElem.GetAttribute("type"));
                ShadowTechnique shadowType = (ShadowTechnique)type;

                mSceneMgr.ShadowTechnique = shadowType;

                int tex_size = int.Parse(shadowsElem.GetAttribute("tex_size"));
                int tex_count = int.Parse(shadowsElem.GetAttribute("tex_count"));

                mSceneMgr.SetShadowTextureSettings((ushort)tex_size, (ushort)tex_count);

                // Shadow Color
                colorElem = (XmlElement)shadowsElem.SelectSingleNode("color");
                if (colorElem != null)
                {
                    ColourValue color = parseColor(
                       colorElem.GetAttribute("r"),
                       colorElem.GetAttribute("g"),
                       colorElem.GetAttribute("b"));

                    mSceneMgr.ShadowColour = color;
                }
            }

            // Scene sky
            XmlElement skyElem = (XmlElement)xd.SelectSingleNode("skyTechnique");
            if (skyElem != null)
            {
                type = int.Parse(skyElem.GetAttribute("type"));
                String materialName = skyElem.GetAttribute("material");

                if (materialName != " ")
                {
                    bool drawFirst = bool.Parse(skyElem.GetAttribute("drawFirst"));
                    float tiling = float.Parse(skyElem.GetAttribute("tiling"), numberFormat);
                    float scale = float.Parse(skyElem.GetAttribute("scale"), numberFormat);
                    float dist = float.Parse(skyElem.GetAttribute("dist"), numberFormat);
                    float bow = float.Parse(skyElem.GetAttribute("bow"), numberFormat);
                    int xSegments = int.Parse(skyElem.GetAttribute("xSegments"));
                    int ySegments = int.Parse(skyElem.GetAttribute("ySegments"));
                    Quaternion quat = Quaternion.IDENTITY;
                    Plane plane = new Plane();
                    plane.d = dist;

                    plane.normal = new Vector3();
                    plane.normal = -(Vector3.UNIT_Y);

                    switch (type)
                    {
                        case SCENE_SKYPLANE:

                            mSceneMgr.SetSkyPlane(true, plane, materialName, scale,
                                                  tiling, drawFirst, bow, xSegments, ySegments);

                            mSceneMgr.SetSkyBox(false, "");
                            mSceneMgr.SetSkyDome(false, "");

                            break;

                        case SCENE_SKYBOX:

                            mSceneMgr.SetSkyBox(true, materialName, dist, drawFirst, quat);
                            mSceneMgr.SetSkyPlane(false, plane, "");
                            mSceneMgr.SetSkyDome(false, "");

                            break;

                        case SCENE_SKYDOME:

                            mSceneMgr.SetSkyDome(true, materialName, bow, tiling, dist,
                                                 drawFirst, quat, xSegments, ySegments);

                            mSceneMgr.SetSkyPlane(false, plane, "");
                            mSceneMgr.SetSkyBox(false, "");

                            break;

                    }
                }
            }
        }

        private SceneNode CreateNode(XmlElement elet, SceneNode parent)
        {
            SceneNode pNode = null;

            // Try to find the parent node
            string pszName = elet.GetAttribute("name");
            if (pszName == string.Empty) return null;

            // Check if this node has a parent
            string pszParent = elet.GetAttribute("parent");
            if (pszParent == string.Empty)
            {
                // Check if the scene node has already been created by a child
                DISABLE_LOGMANAGER();

                try
                {
                    pNode = mSceneMgr.GetSceneNode(pszName);
                }
                catch
                {
                    pNode = parent.CreateChildSceneNode(pszName);
                }

                ENABLE_LOGMANAGER();

            }
            else
            {
                SceneNode pParent = null;
                DISABLE_LOGMANAGER();

                try
                {
                    // Try to find parent scenenode
                    pParent = mSceneMgr.GetSceneNode(pszParent);
                }
                catch
                {
                    // We try to create the parent node as child of root node.
                    // Later when the parent (hopefully) is created, we can adjust it,
                    // if it is child of another node.
                    pParent = parent.CreateChildSceneNode(pszParent);
                }

                try
                {
                    // Check if the scene node has already been created by a child
                    // In this case we would have to change the parent.
                    pNode = mSceneMgr.GetSceneNode(pszName);

                    // Get old parent (probably scene root)
                    SceneNode pOldParent = pNode.ParentSceneNode;

                    // Remove this node
                    pOldParent.RemoveChild(pNode);

                    // Insert us as child on the "real" parent
                    pParent.AddChild(pNode);
                }
                catch
                {
                    pNode = pParent.CreateChildSceneNode(pszName);
                }

                ENABLE_LOGMANAGER();
            }

            // Position
            XmlElement posElem = (XmlElement)elet.SelectSingleNode("position");
            if (posElem != null)
            {
                Vector3 pos;

                pos.x = float.Parse(posElem.GetAttribute("x"), numberFormat);
                pos.y = float.Parse(posElem.GetAttribute("y"), numberFormat);
                pos.z = float.Parse(posElem.GetAttribute("z"), numberFormat);
                pNode.Position = pos;
            }

            // Rotation
            XmlElement rotElem = (XmlElement)elet.SelectSingleNode("rotation");
            if (rotElem != null)
            {
                pNode.SetOrientation(
                   float.Parse(rotElem.GetAttribute("w"), numberFormat),
                   float.Parse(rotElem.GetAttribute("x"), numberFormat),
                   float.Parse(rotElem.GetAttribute("y"), numberFormat),
                   float.Parse(rotElem.GetAttribute("z"), numberFormat));

            }

            // Scale
            XmlElement scaleElem = (XmlElement)elet.SelectSingleNode("scale");
            if (scaleElem != null)
            {
                Vector3 scale;
                scale.x = float.Parse(scaleElem.GetAttribute("x"), numberFormat);
                scale.y = float.Parse(scaleElem.GetAttribute("y"), numberFormat);
                scale.z = float.Parse(scaleElem.GetAttribute("z"), numberFormat);
                pNode.SetScale(scale);
            }

            // Notify
            if (OnNodeCreate != null)
                OnNodeCreate(pNode, elet);

            // Animation
            XmlElement animList = (XmlElement)elet.SelectSingleNode("animations");
            if (animList != null)
            {
                //
                foreach (XmlElement animElem in animList.ChildNodes)
                {
                    // Get name of animation
                    string aniName = animElem.GetAttribute("name");

                    Animation pAnim = null;
                    DISABLE_LOGMANAGER();
                    try
                    {
                        pAnim = mSceneMgr.GetAnimation(aniName);
                    }
                    catch
                    {
                    }
                    ENABLE_LOGMANAGER();

                    // If this animation has not been created yet, we create it
                    if (pAnim == null)
                    {
                        float fLength = float.Parse(animElem.GetAttribute("length"), numberFormat);
                        pAnim = mSceneMgr.CreateAnimation(aniName, fLength);
                        pAnim.SetInterpolationMode(Animation.InterpolationMode.IM_LINEAR);
                    }

                    // Create animation track for this node
                    NodeAnimationTrack pTrack = pAnim.CreateNodeTrack((ushort)(pAnim.NumNodeTracks + 1), pNode);

                    // Iterate all keyframes for this node
                    foreach (XmlElement pKeyframeElem in animElem.ChildNodes)
                    {
                        float fTime = float.Parse(pKeyframeElem.GetAttribute("time"), numberFormat);
                        TransformKeyFrame pKeyFrame = pTrack.CreateNodeKeyFrame(fTime);

                        // Position
                        posElem = (XmlElement)pKeyframeElem.SelectSingleNode("position");
                        if (posElem != null)
                        {
                            Vector3 trans;
                            trans.x = float.Parse(posElem.GetAttribute("x"), numberFormat);
                            trans.y = float.Parse(posElem.GetAttribute("y"), numberFormat);
                            trans.z = float.Parse(posElem.GetAttribute("z"), numberFormat);
                            pKeyFrame.Translate = trans;
                        }

                        // Rotation
                        rotElem = (XmlElement)pKeyframeElem.SelectSingleNode("rotation");
                        if (rotElem != null)
                        {
                            Quaternion qRot;
                            qRot.x = float.Parse(rotElem.GetAttribute("x"), numberFormat);
                            qRot.y = float.Parse(rotElem.GetAttribute("y"), numberFormat);
                            qRot.z = float.Parse(rotElem.GetAttribute("z"), numberFormat);
                            qRot.w = float.Parse(rotElem.GetAttribute("w"), numberFormat);
                            pKeyFrame.Rotation = qRot;
                        }

                        // Scale
                        scaleElem = (XmlElement)pKeyframeElem.SelectSingleNode("scale");
                        if (scaleElem != null)
                        {
                            Vector3 scale;
                            scale.x = float.Parse(scaleElem.GetAttribute("x"), numberFormat);
                            scale.y = float.Parse(scaleElem.GetAttribute("y"), numberFormat);
                            scale.z = float.Parse(scaleElem.GetAttribute("z"), numberFormat);
                            pKeyFrame.Scale = scale;
                        }
                    }
                }
            }

            return pNode;
        }

        private void ENABLE_LOGMANAGER()
        {
            LogManager.Singleton.SetLogDetail(LoggingLevel.LL_NORMAL);
        }

        private void DISABLE_LOGMANAGER()
        {
            LogManager.Singleton.SetLogDetail(LoggingLevel.LL_LOW);
        }

        private void CreateCameras(XmlNodeList list, SceneNode parent)
        {
            // Iterate all Cameras, creating them. We do not attach them yet, since
            // we need to make sure all potential item entities have been created.
            foreach (XmlElement item in list)
            {
                // Ogre could cast an exception, in which case we just try to
                // continue reading the other Cameras
                try
                {
                    // Create camera
                    Camera pCamera = mSceneMgr.CreateCamera(item.GetAttribute("name"));
                    if (pCamera == null) continue;

                    // Set Field of View on camera
                    pCamera.FOVy = new Radian(float.Parse(item.GetAttribute("FOV"), numberFormat));
                    pCamera.NearClipDistance = 5;

                    // Create node with full information
                    SceneNode pCameraNode = CreateNode(item, parent);

                    // Attach the Camera entity to node
                    pCameraNode.AttachObject(pCamera);

                    // Target
                    XmlElement targetElem = (XmlElement)item.SelectSingleNode("target");
                    if (targetElem != null)
                    {
                        // Create node with full information
                        SceneNode pTargetNode = CreateNode(targetElem, parent);
                        pCameraNode.SetAutoTracking(true, pTargetNode);
                    }

                    // Notify
                    if (OnCameraCreate != null)
                        OnCameraCreate(pCamera, item);

                    // Add to camera list
                    cameras.Add(pCamera.Name, pCamera);
                }
                catch
                {
                    continue;
                }
            }
        }

        private void CreateLights(XmlNodeList list, SceneNode parent)
        {
            // Iterate all Lights, creating them. We do not attach them yet, since
            // we need to make sure all potential parent entities have been created.
            foreach (XmlElement pLightElem in list)
            {
                // Ogre could cast an exception, in which case we just try to
                // continue reading the other Lights
                try
                {
                    string pszName = pLightElem.GetAttribute("name");

                    Light pLight = mSceneMgr.CreateLight(pszName);
                    if (pLight == null) continue;

                    // Figure out which type of light we are using
                    string pszType = pLightElem.GetAttribute("type");
                    if (pszType == "omni")
                    {
                        pLight.Type = Light.LightTypes.LT_POINT;
                    }
                    else if (pszType == "spot")
                    {
                        pLight.Type = Light.LightTypes.LT_SPOTLIGHT;
                        pLight.SetSpotlightRange(
                           new Radian(new Degree(float.Parse(pLightElem.GetAttribute("hotspot"), numberFormat))),
                           new Radian(new Degree(float.Parse(pLightElem.GetAttribute("falloff"), numberFormat))));
                        pLight.SetDirection(0, 0, -1);

                    }
                    else if (pszType == "directional")
                    {
                        pLight.Type = Light.LightTypes.LT_DIRECTIONAL;
                    }

                    // Check if the light should be on
                    string pszOn = pLightElem.GetAttribute("on");
                    if (pszOn == "true")
                        pLight.Visible = true;
                    else
                        pLight.Visible = false;

                    // Check if the object should cast shadows
                    string pszCastShadows = pLightElem.GetAttribute("CastShadows");
                    if (pszCastShadows == "no")
                        pLight.CastShadows = false;
                    else
                        pLight.CastShadows = true;

                    // Diffuse Color
                    XmlElement colorElem = (XmlElement)pLightElem.SelectSingleNode("color");
                    if (colorElem != null)
                    {
                        pLight.SetDiffuseColour(
                           float.Parse(colorElem.GetAttribute("r"), numberFormat),
                           float.Parse(colorElem.GetAttribute("g"), numberFormat),
                           float.Parse(colorElem.GetAttribute("b"), numberFormat));
                    }

                    // Specular Color
                    XmlElement specularElem = (XmlElement)pLightElem.SelectSingleNode("specular");
                    if (specularElem != null)
                    {
                        pLight.SetSpecularColour(
                           float.Parse(specularElem.GetAttribute("r"), numberFormat),
                           float.Parse(specularElem.GetAttribute("g"), numberFormat),
                           float.Parse(specularElem.GetAttribute("b"), numberFormat));
                    }

                    // Attenuation
                    XmlElement attenElem = (XmlElement)pLightElem.SelectSingleNode("attenuation");
                    if (attenElem != null)
                    {
                        pLight.SetAttenuation(
                           float.Parse(attenElem.GetAttribute("range"), numberFormat),
                           float.Parse(attenElem.GetAttribute("constant"), numberFormat),
                           float.Parse(attenElem.GetAttribute("linear"), numberFormat),
                           float.Parse(attenElem.GetAttribute("quadratic"), numberFormat));
                    }

                    // Create node with full information
                    SceneNode pLightNode = CreateNode(pLightElem, parent);

                    // Attach the Light entity to node
                    pLightNode.AttachObject(pLight);

                    // Target
                    XmlElement targetElem = (XmlElement)pLightElem.SelectSingleNode("target");
                    if (targetElem != null)
                    {
                        // Create node with full information
                        SceneNode pTargetNode = CreateNode(targetElem, parent);
                        pLightNode.SetAutoTracking(true, pTargetNode);
                    }

                    // Notify
                    if (OnLightCreate != null)
                        OnLightCreate(pLight, pLightElem);

                    // Add to light list
                    lights.Add(pszName, pLight);
                }
                catch
                {
                    continue;
                }
            }
        }

        private void CreateEntities(XmlNodeList list, SceneNode parent)
        {
            // Iterate all meshes, creating them.
            foreach (XmlElement pMeshElem in list)
            {
                // Ogre could cast an exception, in which case we just try to
                // continue reading the other meshes
                try
                {
                    string pszName = pMeshElem.GetAttribute("name");
                    string pszFileName = pMeshElem.GetAttribute("filename");

                    // try to create the mesh
                    Entity pEntity = mSceneMgr.CreateEntity(pszName, pszFileName);
                    if (pEntity == null) continue;

                    // Check if the object should cast shadows
                    string pszCastShadows = pMeshElem.GetAttribute("CastShadows");
                    if (pszCastShadows == "no")
                        pEntity.CastShadows = false;
                    else
                        pEntity.CastShadows = true;

                    // Create node with full information
                    SceneNode pObjNode = CreateNode(pMeshElem, parent);

                    // Attach the mesh entity to node
                    pObjNode.AttachObject(pEntity);

                    // Notify
                    if (OnEntityCreate != null)
                        OnEntityCreate(pEntity, pMeshElem);

                    // Add to entity list
                    entities.Add(pszName, pEntity);
                }
                catch (Exception ex)
                {
                    continue;
                }
            }
        }
    }

    public delegate void LoadedSceneObjectEventHandler(Object obj, XmlElement xmlSrc);

}

Example of usage

OSMLoader loader = new OSMLoader(sceneMgr, window);
loader.Initialize("test.osm");
loader.CreateScene(sceneMgr.RootSceneNode);