Unless you have a completely different operating system in the car, the E815 works perfectly with the BMW. Both my iDrive 2006 330i and my friends 2006 325i without iDrive pair perfectly with my phone. It happens automatically if you set it up correctly.
I have to say that it is NOT easy or intuitive to pair the phones to the car, but once done, it works great.
So, I think your problem is just a pairing problem.
I had trouble too when we got a new Razr. But, ultimately I got it to work.
Now it's automatic.
If you look at the STICKY POST in this forum regarding pairing the E815, you will notice that I corrected the original post and did a step by step approach to pairing the E815.
Try looking for my post. If you can't find it, I'll locate it for you.
Larry in Los Angeles