Question:
Why would a successful ("primo") automobile manufacturer secede market-essential technology which senses, processes, and ultimately manages intelligent driving to a third party, such as Apple?
Two examples of "fail" -- the 
race to the bottom when strategic know-how is simply licensed from others:
- Google as licensor:  the Android market, when reference designs are vested onto multiple licensees.
 
- Microsoft as licensor: the Microsoft-computer (personal and server) market elicits the same results.
 
One is uniquely successful when there is proprietary marriage of hardware and software producing a single, indivisible unit.
In my view, Apple must produce 
fully-assembled, proprietary technology to compete successfully in the next-generation autonomous-driving marketplace -- somehow, somewhere, sometime.  The alternative, simply licensing a plug-compatible overlay to the many will be faced with derision.