Not to mention that realtime traffic data and intelligent routing around congestion is only workable by tracking individual vehicles on the road and recording how long it takes them to get from A to B.
Wrong. There is a better solution, used for traffic lights that adapt to traffic:
Use an inductive loop to count every vehicle and its speed at ever lane of every intersection and exit.
Far lower cost yet, and provides far better data. (Also is totally anonymous)
Um, what? Lower cost to dig up a street and install infrastructure inside it, than to use the cheap and ubiquitous internet and GPS connected computers that are already in every car?
Effectively, you need the infrastructure, most cities on the world have it in some way – either as inductive loops, or by using RFID toll systems, or similar.
So, you have it already, and you can get the same data out of it without the cost of breaking everyone's privacy.