Looks like Continental has a patent from April this year on transmitting messages between vehicles using cellular infrastructure:
"The device (14) has a wireless data communication interface e.g. General packet radio service interfaceor Universal Mobile Telecommunications System (UMTS)interface, for installation in a vehicle (1) i.e. car, and for communication of messages e.g. multicast messages, with other vehicles (2-4). A transmitting and receiving unit transmits and receives the messages over a server (12) e.g. relay server. The data communication interface uses different technologies for transmitting and receiving the messages. An independent claim is also included for a method for providing communication between vehicles."
Another great patent that I found really says something about how original we think our ideas are today without considering what has been done in the past.
The following patent was published in 1926(!), it seems to pretty much cover vehicle-to-vehicle communication as we define it today :)
"The present invention relates to radio warning systems for use on vehicles intended to permit a vehicle to signal its presence by means of .electric waves to other vehicles in its more or less immediate vicinity, equipped with similar or equivalent apparatus and devices, particularly to such vehicles located in front or on the side of the vehicle signalling its presence and facing in the approximate direction of said signalling vehicle."
