With OnStar... Yes LE can get it tracked, even though it is not activated for daily use. It just takes a little longer then calling up and asking for it. Chevrolet has the ability to access any OnStar out there, no matter if it activated or not by the customer or not. Which is actually a little big brotherish really... They can unlock, start the engine, stop the engine, turn on the lights, diagnose, etc... That is, unless you totally disconnect your OnStar unit entirely.
Now LoJack is a great tool to get your stolen recovered. Once the vehicle is entered into NCIC it activates the LoJack unit in the vehicle, and it can be received by LE in the cars that have LoJack receivers. It also gives them a direction the beacon is in, but not a distance. They can be received a long way off, and from the air. Generally a LoJack hit makes cops go nuts, its like fly's on S***.... And generally they don't stop until they find it.