The Lazy method: Make a bunch of prop_dynamics with the respective objects and parent them to the track_train.
The Extremely-Tedious-Yet-More-Rewarding method: Compile a new model with a tutorial not unlike this one:
[ame="http://forums.tf2maps.net/showthread.php?t=838"][TUTORIAL] Complete Guide to Adding Custom Objects to your TF2 Map - TF2Maps.net Forums[/ame]