Calls on iP4 mutes BT when using TT
 

It is a disappointment that BMW gave up their best maps because the 2011 nav dvds for my 2008 X5 are vastly inferior to those in TomTom (plus 2 dvds now required). My $50 TT app not only gives better routing but real-time traffic reports.

When a call comes in on my iPhone4, I lose the BT connection to the X5 speaker and have to pick up the phone to hear/talk.

Is there a solution and if so is this likely a TT setting or something I need to take up with BMW when I take it in for routine maintenance next week?