**** it doesn't. My wife bought a 920 (mine is in the mail ) and WMP sync is horrible. It is converting all m4a rips to wma even when I turned off the audio conversion and then it strips out all tags. So my only real option is the primitive Windows Phone desktop sync app.
I don't mind, it works. If the Xbox Music App needed to do that I would be more than happy, I just want it to work.