Yes, you can disable the service; however, it's my understanding that you can't remove the equipment without setting off a ton of codes.
To disable, remove the antenna (slide to side and remove) and pull the fuse...viola...no omre comms with OnStar
Simplest way would have been to order the car without it in the first place.
If you're not interested in it. you may be able to have the dealer or an aftermarket service company, uninstall it for you.
I wouldn't worry so much about OnStar reporting your errant ways
as I would the CDR, (Crash Data Recorder), normally referred to as the "Black Box."
It generally records the last 5-15 seconds of an event for accelleration, braking, yaw, position, blah blah blah blah.....
Law enforcement, and insurance companies may access this information. You (and the other guys) insurance company at will.
Law Enforcement with a subpoena.
Removing it will not only void the warranty, it will (IIRC?) disable your passive restraints (airbags and such). Doing this does a couple of things:
1) Voids the warranty
2) Likely violates Federal Law (have to research it again but I believe that's the case
3) Sets you up for SERIOUS LIABILITY issues in the event of a crash where anyone else, either riding in your car or another car, is injured. (Sets a presumption of your intent to violate the law)
4) Eliminates or seriously impaires your opportunity/ability to recover damages if you're injured in the car, even as a result of someone elses negligence.
I'm sure I missed something, but you get the drift
And by far, that CDR and you OBD system are your biggest enemies when it comes to dealerships and thier warranties.
Hope that helps some.