Just thought I'd update this as I was also looking for info on this.
I can confirm that with a $19 Y-Cable from ebay, and a Gen 4 Ipod Touch (running iOS6) - Spotify plays perfectly through the i-Drive on a 2010 E92.
No jailbreaking, added software or any tricks needed.
The song appears on the screen, with all details relevant to the song playing and full steering wheel controls control the ipod action.
Here's some pics to illustrate:
..sweet torquin' diesel!
Last edited by QLD; 12-03-2012 at 04:00 PM.