I am fine with that kind of system if:
- data is only sent to emergency services
- data is only sent when required (crash detection, airbag deployment, manual call through button etc)
And it is unrelated to all the data the manufacturers collect.
How do you know? Did you set up a fake cell tower to MitM the communications? No? Then you actually don't know.
I am talking about the theory. I don't have a car.