Multiple Fobs for multiple cars

We have a 2006 Prius (Package 5, Green), I'm now about to pick up a G3 2010 V with Nav in Blizzard White as well. The dealer has notified me it should be in next week. Does anyone know yet whether the SKS on G2 and G3 are compatible? If so, and it is true what has been said in other threads that you register the fob with the car, not the other way around, then can you register new fobs, (or old ones) to multiple cars? If so, I could carry one fob that would work on both cars, and we would have four fobs that would work on both cars. Is that possible? Thanks.