you could try fix up uvs on the low poly save it out as an obj from maya or max(?) then in mudbox you go down to the lowest subD level File > Import UVs Select your fixed uv'd lowpoly obj that you exported then the model in mudbox should take on the new uvs and you can jump back up through the subD levels
Sorry for the cryptic thread title, attempting to fully write it would make it too long. I'll just explain in my post. Low poly model UV unwrapped, then brought into Mudbox for high res sculpting, normal baking and 3D texture painting. Model subdivided up to level 5. Proceeded to sculpt at the highest level, and then…