Yip, have iphone and have experienced this a few times, it's the same sound you hear when your mobile is too close to landline phone, (especially conference phones). The freakiest thing with the fiscon is when you disconnect the iphone from the MDI cable and it syncs up with the fiscon bluetooth audio connection and the music carries on, albeit quieter and only through the front speakers.
Not sure what causes the interference but it goes away if I put the phone in the drivers side door pocket.