Are you saying they can bring a new data center online without any connectivity to the rest of their infrastructure? GP isn't concerned about turning on one data center, they are concerned about turning them all on at the same time, and that can never be tested.
If you practice bringing a new datacenter online without any connectivity on the existing deployment, and you practice then joining two disjoint "clouds", then you've pretty much covered your bases.
Are you making a rate limiting/ddos argument about "turning them all on at the same time"?
IIRC some of the information about their approach is considered sensitive so I won't elaborate further.