You'll be pleased to know I'm now the proud owner of a gently used iPhone 3GS, jailbroken and unlocked so I can use it with the T-Mobile PAYG SIM from my Z520A. Actually I'm the proud owner of a gently used iPhone 2G as well, at least temporarily. But as to why I now have two iPhones is maybe a story for another day.
Anyway, I've got it paired with my car and it works beautifully. The Bluetooth on it, of course, doesn't interfere with Carwings, and the handset phonebook uploaded to the car as you would have expected it to. Heck it even shows up as a Bluetooth audio device. And, of course, the first App I downloaded was the one for the LEAF. Life is good!