http://www.youtube.com/watch?v=Duf0AIySsA8

I make a video (sorry for my bad english)

Thanks for watching and for your answer

A. They are vertex textures (only meant for models)
B. They are in fact the UV mapped textures for some of the models for the 'Super 8' special preview map included as part of Portal 2 as a promotion for the movie. They are only intended to be skinned to those specific models and I have NO idea why Valve has these particular vertex textures in the editor.

So, in short, never use them. (or textures with _vertex after their name, for that matter)

As I suspected those are vertex textures, commonly made for and used by models.

This is what's inside traincar_shelf.vmt:

VertexLitGeneric
{
$basetexture "traincar_interior/traincar_shelf_C"
$surfaceprop default

$ambientocclusion 1
$envmap env_cubemap
$envmaptint "[.01 .01 .01]"
$envmapcontrast 0
$envmapsaturation 1


$rimlight 1 
$rimlightexponent 1 
$rimlightboost 1 
}

Suggestion: take what you like from those textures (the part you like), export it and make a custom texture with a normal (LightmappedGeneric) shader.

EDIT

Damn it! this is the third time today someone post before me! Am I losing typing speed on vacation?