The patent filing, which you can view here, describes the system as being primarily intended to "improve the drivability of a sports car in conditions of poor grip," not necessarily to improve the vehicle's green status.
Ferrari’s design eliminates the associated heavy weight of 4WD vehicles by using two powerplants in the car – each to drive a separate pair of wheels – which in turn eliminates the need for heavy and bulky transfer cases and driveshafts. In all the designs, however, the engine is matched to an axle via a locking differential.
The design is similar to PSA Peugeot-Citroen’s hybrid system in that it separates the roles of the engine and electric motor. Furthermore, Ferrari has submitted six different layouts for the patent, with some of them calling for the electric motors to sit within the wheels instead of on a conventional axle.
When applied to one of Ferrari’s cars, the system will likely feature an on-off switch that will allow the driver to decide whether or not they want standard RWD or the added safety of 4WD. The system will also allow for electric only propulsion at slow speeds, which will vastly improve Ferrari’s carbon footprint and position in the eyes of environmentalists.
What wasn’t revealed was any possibly launch date for the system but given its advanced nature we don’t expect to see any production 4WD hybrids for some time to come. Speaking with Car and Driver, however, CEO Felisa said the concept would be coming soon. "Not at Frankfurt," he said, "but shortly thereafter, probably at an American show." That times it right for a Los Angeles Auto Show debut, which is the last major auto show of the year in the U.S.