I've tried it also with my mom's 5310 and worked perfectly. A2DP doesn't turn on unless you add the radio as an audio device I think.

The bug is in the N9 as it's not logical to switch to an A2DP stream when there isn't any playback going on. If I hit play in the music player it does switch to A2DP again and that is indeed correct.

I think the confirmation sound harmattan does when the "connected to x device" sign shows has something to do with this. Is there any way to disable that sound and see if it stops switching to A2DP?