Having another crack at the audio.
I'm now assuming that its headerless xWMA. I'm currently trying to use xWMA encode
to produce a valid xWMA file from a wav, then chopping out the data, correcting the wav size headers, inserting the data from one of the MI WMA's and seeing if xWMA will decode it back to pcm wav. The trick is in finding the correct bitrate for the input and output audio.