eth: garmin and other traffic monitoring GPS units get their information from local radio bands or over cell phone networks, not over the GPS network. Even TomToms communicate through radio to each-other directly to share information on traffic times and map updates. If it was over the GPS network they would be able to give your traffic everywhere, not just near major cities. Most GPS units do not transmit information to the satellites, they rely on a table and the time signature/ID from the satellites. Depending on the positioning of the satellites, with their time stamp, it can triangulate your position based off of the table. It is was not this way then you could get your position off of 2 satellites, but as it is you need 3 or more, and there are a growing number of dead zones as satellites drop from orbit without being replaced. Please remember GPS is really really old technology and was not made with the capacity to track things without augmented hardware. Most (though not all) GPS tracking systems are just tracking systems with a GPS antenna which must have their data retrieved over the cell network, radio broadcast, or physically removing the device and plugging it into a machine. Even if you believed that GPS units allowed gov't agencies to track you, you can go buy a unit with cash and they would have no way of knowing who bought the unit. I am all for erring on the side of paranoia, but know the limits of tech. It is much more limited than governments would have us believe.
Second, we are all being tracked (or at least have the capacity to be tracked) here in the US through the cell phone network without it being a problem, it is little surprise that a Communist gov't that does not believe in personal rights would do this as well.
Third, I am a little surprised that cell phone tracking data would be accurate enough to help traffic congestion. It is accurate to within about a 1/2-1/4mile of your location most of the time. But then again when a country has week long traffic backups I suppose it does not need to be that close.