Not mentioned in the article, but perhaps a relevent comment on the privacy concerns: In the UK at least, the government have already installed license-plate tracking cameras on overpasses on almost every major road in the country. Sniffing the RF V2V data wouldn't really reveal much more (apart from speed).
I suspect that it would be politically unacceptable to routinely prosecute for speeding offences that were identified with this data (although perhaps there would be a grey area when very high speeds were identified).
It could transmit everything collected by your car's event data recorder. This includes information about your car maintenance, current seatbelt usage, derivable information about how much weight your car is carrying, etc. It basically creates a data channel between any onboard computer in your car to a wireless network.
I suspect that it would be politically unacceptable to routinely prosecute for speeding offences that were identified with this data (although perhaps there would be a grey area when very high speeds were identified).