Partnering with Apple to handle the phones and other customer facing? Okay, I can sorta see the benefit to Tesla in terms of drawing on experience, but I seriously cannot see Apple selling that as a service. And, in the long run, Tesla is better off investing in their own people and processes.
If, instead of a sold service, it was a partnership where Apple took over the user part of the car and customer interactions so that they could collect fees for Apple music, etc.... Okay, that would be a partnership. But would it be mutually beneficial? I think not, Tesla would be creating an external dependency (like the Adobe/Apple relationship, where Apple could constrain Tesla based on Apple's agenda) such that any benefit would only be near term. In the long run, Apple would benefit by gaining a revenue stream from Tesla and the ability to exert influence.
But that would be one-sided and not mutually beneficial.