The innovation of this service is that there are no designated parking stations. Instead, registered users can locate the nearest available vehicle, finding it by simply using a phone. The cars possess a GPS unit that makes the location available to the system. Users then have to pass a user badge and start rolling. The council guarantees that there will be a vehicle available closer than a three minute walk from the user's location. You can watch a video that was broadcasted on LC1 at this link (albeit in French and after some advertising) showing how it works.
The experience is, however, somewhat limited. Antibes is not a very big town and the service only includes 5 cars. The cars are quadricycles (that is, you need no driver's license to drive them) that, instead of an anemic 2-stroke engine or tiny diesels that quadricycles are usually equipped with, have been converted to run on electric power. This is the reason why the car can't run on highways or national roads. There's another limitation: they can't go more than 10 km (6 miles) outside the city. Other specifications about the vehicle aren't yet available on their site.
Nevertheless, these initiatives show that there is another step to take in carsharing. Making electric vehicles available is just a very nice icing on the cake.