what?
Quote: "if you know how to write shaders, you could make some kind of motion shader that makes it look as if the trains is moving, while it's only the textures moving"
Not in FPSC you can't. What are you going to write the shader IN? FPI scripts? I don't think so!
also
Quote: "In your script you can add an effect.
The effect scrolls and image across the surface, search around in the effect area after hitting add effect in the segment editor"
That's just plain rubbish! There is no shader in FPSc that does that. Why not just admit you don't know rather than giving this poor guy a bunch of false information!
You could make this effect by making a decal that scrolls a wall texture. You then scale the decal to the same size as your wall and place it outside the train window.