Tracking our vehicles has been something the government has been involved in since liscense tags were first introduced. The array of technology that is at their disposal makes that much easier, but most people's daily activities are not of concern to the government, however, that could change at any time.
Right now I do not believe that the government is trying to track our vehicles. However, as ISIS and other terrorist groups infiltrate America, the government may want to track vehicles to make it easier to track where terrorists are in the immediate aftermath of an attack. It may also be necessary to track people who raise certain red flags within government organizations.
No, the government is not tracking us by collecting data through our vehicles. There is some information that might be useful to the government, such as mileage, rates of accidents in certain areas, and consumer buying habits, but these are for aggregate statics and not for determining the location or habits of individual drivers.
The government is too bureaucratic to be able to track vehicles. They can barely keep up with tapping terrorist phone lines. Now, I'm not saying that there are no specific vehicles they may be monitoring for covert operations but they can't do it for all of us, so I would not waste time worrying about it.