To me it seems that this event is exceptional in many aspects. It would be more interested in the survival aspects, after the landing. I agree that there was almost no time to let c/c or passengers know that a ditching will be performed (and even if they knew, would that have helped, or on the contrary, create more confusion?). But apart from the aircraft having sustained the impact rather well, the key factor in the happy outcome was really the immediate assistance by the Hudson boats/ferries. The ideal place to go!