I read the following information about the latest release of the FBX file format on Autodesk’s site:
Does this mean that the target game engines would handle subdivision on the fly? Is this something that Unity could handle?
If you’re interested in reading the rest of the posting, go to this link: http://area.autodesk.com/blogs/shane/fbx_2010_2_update
I tried that, but it doesnt seem to work, I have a low poly model, then I rigged and animated the bones, then I applied subdivision to make the model geom at high resolution, and export it using FBX exporter 2010 for maya, I checked all the smoothing options, then imported it in Unity, it is still in low poly 
Its something that would need to be supported in the technology, if it isn’t, it does not work.
Its nothing that works automagically.
As Unity does not offer any integrated LoD solution to allow you integrate your own, so handling the data wouldn’t make too much sense.
FBX 2010 is currently not supported actually, its currently on 2009.x from what I remember