Vertex maps arn't stored as textures but as vectors assigned to the vertex numbers on the geometry, you could probably script something that does this relatively simply but seems a bit of an over kill. Does fbx not support this ?

If its stored in an fbx that might work, if not its possible to convert vertex maps to file textures that can be read into other scenes. Max might have something that can take a file texture and turn it into a vertex map, as long as you can get the file out from maya (i've only ever used it in the n cloth context, its in the nMesh menu I think).