Collisions with BSP

I have a BSP file in Quake 3 format which contains world geometry of the room. And I have a mesh file which contains a model (a box for example). I load my BSP file in OGRE using the Plugin_BSPSceneManager and load my mesh using the createEntity method of the manager. Then I create a CollisionShape for my mesh (for example BoxCollisionShape) and a RigitBody which uses this CollisionShape. It works well but the body does not collide with the room (loaded from BSP) and I don't know how to get information about world geometry from the SceneManager object to create a CollisionShape from it.

Please, suggest the solution of my problem. How can I get the CollisionShape of world geometry or how can I make my model to collide with world geometry loaded from BSP in other way?

Thanks.