Multiple BT phones?

How many BT phones does the X3 support (2009 model). More than one? Is there a way to define priority at engine start?

Put another way: two cars: '09 X3 (wife's), '05 ///M3 (mine). Two iPhones. I'd like both phones paired with both cars. My phone should be the primary one paired in the M3 if both phones are in range when engine starts, but my wife's phone should still work if mine is not present. And vise versa. Does this make sense? Can it work this way?

I have a generation 13 ULF I don't know about the TCUs but on mine it supports 4 devices and it's first come first serve.

Pair her phone first, then yours on the X3. Do the opposite in your M3.

Good choice of cars BTW!