IIRC, this is something that WMC just does and channels it back through the MCX session.
I found that it works OK for music, but not as well as a real DLNA DMR.
My take is it's been frozen for years. The Echo was announced over a year ago and if it was a viable market it would have shipped long ago (they would have invested the time and resources to do such). By all accounts (product wise) it was released way too early... I think they decided to punt and recoup what they could before they can't even give them away for free.