I tried to make a raised but flat area for a high-level station without raising the terrain. To do this, I made an area of the correct size using TACS/GMax, textured it as required, and raised it to the correct height. I then laid the required track on it, raising the splines to the same height - a bit of a fiddle, but it worked, and provided the area of the raised asset was large enough, a complete station could be laid down. In the same way, platforms and buildings etc. could be raised to the same height for placing.
The raised base thus created need be no more than a single-sided plane, all of two polys, with the texture used 'tiled' to look right.
This could perhaps be of use in creating a narrow, raised area for straight track with the ditch on each side?
Ray