Best to ask about this in the [UMA thread]( UMA - Unity Multipurpose Avatar on the Asset Store! (Part 1) page-164).
But basically, two things I could say right off the bat: 1) Mixamo creates FBX for Unity animations that work with mecanim, so they should work with UMA, and 2) it seems you should be able to use the base male or female UMA FBX in the Mixamo animator.