It'll definitely vary widely. Plus side of Kia being a stupid penny-pincher is that in my lower trim model it has no cellular radio that I can tell. But of course I'm planning to get rid of it so I've been eyeing a Toyota (4Runner), older 3G equipped models are obsolete in terms of the data tracking here, newer ones you can fiddle with the "Data Connection Module" (DCM) by fuse, antenna (although that's not completely effective), and generally it's a clean disconnect by fuse except it'll kill the microphone. In the rent's Sonata I believe the BlueLink bits are tied to the headunit.

Looks like something to keep an eye on in the future, hopefully more people catch on and are willing to tinker. Read about some wanting to pull apart the dash and wrap the DCM in foil but haven't heard of how that goes. There's also the option of calling(?) Toyota to turn it off, but whether it can be reenabled remotely is another question.