Facial animation in maya -> unity

Personally, I've only use skeletal animation for faces in Unity- but recently it has been brought to my attention that Mega-Fiers (a unity modifier bundle on the asset store) now allows you to bring in morph targets. I've never used them myself- but they may be something you want to look into.

Otherwise, no- there's no way to do vertex animation in Unity.

Joint based facial animations are both a relatively straightforward Maya rigging solution and likely the best bet performance-wise. Requires an artist's study of the face's muscles and bones and detailed attention to weights painting in Maya. But after that results can be surprisingly good without deeply sophisticated rigging or middleware.

just make sure you select "bake animations" when you import your animation or your animation will never activate.

MegaFiers now has a Maya exporter for Blend Shapes making it very easy to add to your Unity project. http://www.youtube.com/watch?v=gCVUvDBL5Gc

Since 4.3 unity supports blendshapes natively, just copy in the FBX. Blendshape curves can be animated with the faceshift plugin, I've put a tutorial on http://www.youtube.com/watch?v=iKaLSteP77g