You normally always have a secondary routing just in case such an incident occurs. It is basic design of an essential system. It isnt just messages between families and emails there is a lot of business traffic going over the network as well.
If it is a server, again on an important system you always have several servers all looking at the same traffic. Should one fail, and they can, another server which has been also gathering the information but not acting on it comes into play.
On such as system as 3BB it is very poor design to have a single failure take the network down.