This is made out of solid brushes tied into a func_tracktrain even in opposing force! I can post an example map if you want!
And I think even in opposing force you can't tie a model to an entity!
but you can tie sprites to a train_sprite. The
vlatitude has a nice fgd file for opposing force!
Unfortanetly it was desined for worldcraft 3x so it can't view entities!