I have a cable for the minicooper that plugs into the phone and splits into two -- one usb and one headphone jack. those plug into the car just under the shifter.
in ios 6 (and some earlier ios7 betas), the map programs would use the speakers of the car, muting the music to announce a turn or whatever.
now, the map programs work just fine, there's just no sound that comes out.
but oddly, i can play music just fine.