To me, it seems much more likely that an Apple/Tesla meeting revolved around Apple wanting Tesla to offer an iOS powered in-car computer, as they've just done with the other carmakers.
Apple could also be buying Tesla, of course, but I can't imagine Apple not at least trying to get Tesla onto iOS. Though I also can't imagine a world where Tesla would agree!
There is zero chance of Apple buying Tesla. It's either (a) iOS in the car as you said or (b) co-investment, patent sharing or technology sharing between the two companies.
Apple could also be buying Tesla, of course, but I can't imagine Apple not at least trying to get Tesla onto iOS. Though I also can't imagine a world where Tesla would agree!