The map a func_train? Oh man no! Put moving objects in the 3D skybox instead. If the whole map is one entity you'll have a very hard time keeping performance low (or, getting a reasonable amount of detail in the map). The problem is not the unavailability of func_details. It's the lack of VIS for entities.
Bytheway, dismaps aren't moveable, but models can be animated... There's a guy who made a map aboard a cargo ship, with a moving landscape (and bridge) around it, modelled. Looked pretty neat.