This rumor broke a while ago so I don't remember the exact details. But essentially what I found when the rumor did break was that Apple had hired lots of engineers who specialized in the automotive industry. I looked at some of the LinkedIn pages and these engineers specialized in things that had basically nothing to do with Carplay. It was claimed that Apple hired tons of these engineers, too many for Carplay to justify, but I never looked at every single LinkedIn page to confirm. Also, most famously, several vehicles were spotted around the bay area that had license plates connected to Apple. These vehicles were outfitted with arrays of cameras an possibly LIDAR. I assumed that there was no LIDAR to be safe. In my judgement the quantity and positioning of the cameras indicated very strongly that they were a part of an autonomous vehicle system, not a street view program or anything else I could think of at the time. Then there were the anonymous sources. They claimed that Apple was working on an EV and that its development was referred to as Project Titan internally. I guess that should be taken with a grain of salt. The most convincing thing for me is the broader picture. Apple has a lot of experience and expertise in power electronics. It has manufacturing prowess even if it is through 3rd parties. And it has a huge amount of cash that is sitting around waiting to be spent on creating the next big thing. And most importantly Apple recognizes the fact that there is an EV revolution approaching. The motive, means and opportunity all line up for the Apple EV. All of this makes me give some weight to the rumors but no, nothing has really been proven with hard evidence yet.

Some stuff here http://www.macworld.co.uk/news/apple/will-apple-make-icar-pr...