Per Tom at Icelink you need to use the Sirius from BMW, NOT an aftermarket Sirius kit.

The aftermarket kits emulate the CD Changer, which the Icelink does as well, and the data bus can't handle TWO devices that look like CD changers. Since the BMW Sirius shows on the data bus as a different device than the CD Changer, no conflict occurs.

(As long as you don't have a CD Changer too : )