It's not the shader that's wrong (well it might be, but that's not your problem so far). Yes, you only have flat surfaces, but polygons are always flat. Look at the smooth lighting on your tracks. That's because the vertices are all welded together. Normals get interpolated between vertices to make things smooth.

You want flat-shading, and to do this you need hard edges between each flat surface. And to do that, you need to detach them from each other. And to do that in MED you want to copy a flat surface, delete it, then paste it (it will have the right position, but not be attached to the surfaces around it).

Jibb