It's the other way around: they phone home so that they can be bricked, or at the very least have important features disabled at Tesla's whim.

What you're suggesting can't work because there isn't cell reception everywhere, but of course that hasn't stopped car rental companies (I think) implementing exactly that with the predictable result of people being stranded in remote locations.

The real danger is that someone from Tesla is here reading your comment and putting it on the to do list.