For Subway Cars: Gmax,3DsMax,Autodesk Inventor or some other 3D modeling program.What Strain is using is sketchup which works as well.
As for stuff I supposed non-rolling stock items I recommend u reskin stuff on the DLS if not use one of those programs.
@Green Eggs mind sending me the complete MUS pack please(platforms,walls,tunnel,track etc...)thanks if so Subway7695@yahoo.com if not its ok.