BMW NA should cover your car rental if you're still under your full warranty. According to the dealer I go to, BMW of Greenwich (CT), they say BMW NA covers rental fees up to $44/day. I had a rental for 10 days for my 07 and BMW NA covered $44/day and I paid an extra $10/day to not have to drive a VW Bug.

Edit: BMW of Greenwich exclusively uses Enterprise. Not sure if this is just them or BMW NA mandated. Also, maybe this is only BMW of Greenwich's policy but my SA said BMW NA covered it. Duno.