Yeah, initial plan was to use game engine of our developer friend 3Dvision with simple Direct3D engine. But at that time (2008) Ogre started to have ecosystem of tools, is feature-rich, etc.
As I said we had regular PC configuration with GeForce videocard as target. We have delivered the game controlled with mouse and they then added support for mounted guns. From what I have seen, they used some shared memory library to read state of hardware. The memory region was probably updated by device driver of the controller. If you would like to build a coin-op nowdays it's quite simple, there are eshops where you can buy every component (various designs) and just put it with some PC together.
This project was finished with a little loss, because direction of the game was changed severaly. It meant to be for different type of machine at the start and also Asian people like to copy other games, so we were always told "Look at this, we want it to have such feature in the game!" The good point is that we are not longer afraid of competition and cheap labour from this area