I've upgraded my Phone and my car since my last post about a quite similar but very specific phone-car combination. Unfortunately, this one isn't about eventually triumphing over my own stupidity, but two observations.

1. Since upgrading my iPhone 4S to iOS 6, I very occasionally get the following problem. I plug the phone in via a USB cable, select it as the input source, and start a track playing. Despite being plugged into the car, and controlling the device via iDrive, the audio inexplicably plays out of the phone. Unplugging the phone and plugging it back in doesn't seem to help. Stopping and re-starting the car does seem to fix it, though not always. It doesn't seem deterministic at all—I don't know how to make it happen at will, and I don't know how to fix it reliably.
2. iOS 6 was supposed to bring email and SMS integration with iDrive, among other features. I upgraded the car's Bluetooth software to the latest version available, and yet I get none of the new features. I've set "Show Notifications" to on in the Bluetooth settings for the car on the phone, but under iDrive's "Office" screen, all I get is "Contacts" (which has always been there), not "Current office" or "Messages", where the new features are supposed to appear.