When Google Maps came to the iPhone, I played with it on my wife's phone and noticed that directions came over bluetooth, interrupting any music that was playing. When I got my Razr M, I presumed the same would be true, but unfortunately it doesn't seem to work and only comes through the phone speaker. However, yesterday while using navigation and on a phone call over bluetooth, the voice prompts for navigation came over the speakers in my car so it would appear that it's possible for the Navigation commands to come over bluetooth. The question is why don't they? I've got a Razr M on version 4.1.1 and I'm using this in my 2011 Mini Cooper.

Any suggestions would be appreciated.