Afraid I can't help directly, this stuff too complicated. But I can confirm BT works as expected (i.e. audio source automatically switches between phone and AM/FM/CD/Aux) in my '09 with iPhone6. Did you try pushing the phone button on the steering wheel, then does the car say "Ready"?
Yes, the car did say "Ready". I didn't try dialing, and I have no reason to think it wouldn't work.
I imagine how it should work is,
1. bluetooth is connected;
2. Audio (Radio or XM or HDD) continues to function as normal;
3. a call comes in, ring, ring ...
4. hit a button to answer the call, then audio is muted;
5. when the call finishes, hang up the phone, audio continues ...
I just can't get the audio to do anything after the bluetooth connect