Andrews and Arnold have taken some measures against disaster with the separate independent domain name aastatus.net which I think is hosted by their friend-company Watchfront, and they also iirc use Watchfront’s network for disaster-redundancy [or whatever?] where needed. Watchfront is their collaborator in firebrick.co.uk. I have this very vague dubious memory about AA using Zen’s network for some disaster measures - is that utter nonsense that I just dreamed up?
I was thinking that Facebook need a completely independent, second, parallel management network, which also has a route into the main management network and their normal AS. But they need second interfaces (maybe not physical ones) into switches, routers, critical servers, so they can monitor and configure them even when the main AS is dead. It would be a nightmare to implement and test and would cost an absolute fortune, but they can afford it.