> So maybe there is a plan, or maybe they just designed the system in such a way that they could convince themselves that it would not go down unless things were so severe that loss of the phone system would not be your chief worry.

My belief from working in very large companies, and (previously) in mission critical systems is that a clean bootstrap and recovery process is extremely unlikely, almost impossible. Because in complex systems full of legacy parts and people who have long retired, the stars won't align.

The only way to truly know is to design and periodically test for disaster scenarios (emphasis on the plural). But due to the scale in time and space, cost and bureaucracy, this planning and rehearsing is not going to happen with the desired detail and intensity. People do not seriously plan for things that have never happened.

If it does happen, there will be a small group of extremely capable people that will find a way to bootstrap the system. It won't be according to some previously laid out plans -- they will make the plan in real time. They're not famous and probably never will be.