So, I finally got a chance to take a look at the behavior in my car, and drum roll... N9 shows up as a MirrorLink device, and the 'Car Mode' apps show up on the touchscreen in the car, but attempting to start any of the apps seems to lead to... nothing, except a message that an app couldn't be started, and basically I just get an empty screen in the car.

The apps do appear to run on the phone itself, but something seems to be broken or out of spec.

Also, the behavior above is what I get when the car is parked, and if I actually start driving, all of the app icons are muted, and the apps are essentially disabled because they haven't been certified for use while driving, etc...

After all the dust settles, the N9/phone integration in my car (2016 VW, Discovery headunit, IIRC) makes MirrorLink and Car Mode on the N9 look like antiquated, unsupported junk, and the 'native' phone/carkit integration is actually very good without MirrorLink, Bluetooth pairing only, access to contacts, call history, A2DP audio source, reading/composing text messages on the car touchscreen, etc...