I've started looking at some of the Mac P2 bugs and started with the Bluetooth one, ID 167.

The problem is easy to reproduce and is down to this line in AudioIS::StartStream

   if( playbackTracks.GetCount() > 0 )
      playbackChannels = 2;


   bool successAudio;

   successAudio = StartPortAudioStream(sampleRate, playbackChannels,
                                       captureChannels, captureFormat);

My bluetooth headset, like most, is mono.  Setting playbackChannels to 1 cures the problem and I get playback, but I'm not sure how to test for this condition programatically.

Any advice welcome, I can give it a try and report back.