This is not a bad idea, but it may be overly complicated and expensive. Automakers and suppliers, including my own employer, are actively working on engine start-stop systems which will prevent long engine idling by shutting down the engine if the vehicle comes to a standstill for more than a few seconds. The engine is then restarted when the driver lifts off of the brake pedal. It sounds like the IBM proposed system would save a few seconds of idle time per car, and perhaps schedule a smoother restart, but at the cost of additional electronics at each intersection, and in each vehicle.
There is also a question about consumer acceptance of the traffic signal system being able to shut down your car.
