Not sure on the bluetooth profiles being used. Under options on the phone I see a check box for media audio and phone audio. I have tested with both checked and just phone audio checked. They both give me the same results. The phone is using Android "Gingerbread" 2.3.6. I haven't picked a frontend yet. This still a work in progress. My test thus far used Windows Media player on a Windows 7 (64) PC.
Oh I see. Well no bluetooth stack I've ever seen will mute/pause music playback during a phone call. This is more of a front end or software plugin function. This would be something to keep in mind when looking at frontends. I know not many of them support this function out of the box but there are quite a lot of plugins to do that very thing.
I'm not too sure anymore which frontends do this. You'll probably have better luck researching this and testing it on your own to make sure it works for you. Not all frontends and plugins work with all phones out there.