Well, keep in mind that the reason Apple requires vehicle-provided GPS for wireless carplay is for a better end-user experience, not due to any technical limitation. The vehicle's GPS will almost definitely be more accurate, and using it greatly reduces the power demands on the paired iPhone.
So Apple "requires" vehicle-provided GPS for manufacturers to certify their Wireless Carplay implementations. Apple won't allow them to advertise Wireless CarPlay if they didn't implement Apple's spec.
But that doesn't mean that Apple would *prevent* CarPlay from using the phone's A-GPS in the absence of vehicle-provided GPS. On the contrary, Apple has every incentive to fall back to that because there are cases where the iPhone would provide better location data than the car would (like in a parking garage, for example).
Intuitively, it seems that CarPlay (both wired and wireless) has been designed to first look for a GPS signal from the vehicle, and in its absence fall back on the connected phone's GPS signal.
As for the Pioneer 3D Calibration thing, I think that's more to supplement its own GPS than to be used in lieu of it. GPS radios are cheap now--it is not a large cost for manufacturers to include it. I would think the 3D Calibration would be more for trying to get more accurate heading data, something that GPS alone can struggle with. That said, I've not looked into it myself. But I really doubt any head unit manufacturer would be looking at using it instead of a GPS chipset at this point.
