So far, in all of the other games I've worked on, the game level editor used light sources that were placed within the game engine.

The Lord of the Rings game I worked on, did in fact use vertex lighting, but it wasn't something that we did in Maya because our environments were modular... that is, we'd be using the same set pieces of hallways and rooms to form our dungeons and so on, so Wall1 had to be able to be lit differently throughout the level. So, we placed lights within the game editor and the editor actually would bake the vertex lighting into the modular pieces.

Vertex lighting from within maya is only applicable really for set pieces that are only going to be seen once from one lighting setup so it can be baked down before exporting. Unless you are given room to have, say, 3 versions of an area... day, night, dusk for example. In which case, you'd export 3 different models all with different lighting applied.

Hope that makes sense.