Are you guys using the single-DIN or double-DIN head unit? I have the single-DIN Alpine iDA-X305 in my Roadster, and using the Apple USB to Lightning cable definitely does NOT work. There is a note about the incompatibility issue on Alpine's website (as well as other forums). According to the notice on the website, using the Apple 30-pin to Lightning adapter does work. I have a non-Apple adapter that results in the same "USB Device Error" message as the USB to Lightning cable, and I would like to verify that the Apple branded adapter works before wasting another $20. The resulting stack of adapters is not pretty, so I hope this is just an interim issue.
Based on the details, I would hypothesize that the X305 Alpine head unit doesn't support digital audio over USB, only analog (which the 30-pin to Lightning adapter provides via an onboard DAC).