Originally Posted by PaddyMcGrath
I'm pretty certain you won't be able to access - or at least hear Siri back - when listening to the radio or a CD however.
If everything's working right, that's not true - as soon as the handsfree profile is called up by any paired device, the radio switches speakers over to the handsfree output and makes the car's mike the handsfree input. It doesn't matter what source the radio is set to, since (if everything's working right) siri isn't sending audio to the aux in, it's sending it over bluetooth handsfree. You can tell this is true if the siri audio quality is noticeably crappier - the handsfree profile has severely limited bandwidth.