I don't buy this argument. If a service needs another service running on another server which is not already available, it should retry with an exponential backoff. Doing anything else is a bug.
I remember having read somewhere about some company (Facebook/Google/Amazon/Twitter/Dropbox or something at the same scale) that regularly simulates a whole datacenter failure, which made believe it is possible to automatically recover from this.
Are you saying that even the companies I mentioned have the same issues as OVH when they recover from a complete power failure?
It was Google: http://queue.acm.org/detail.cfm?id=2371516 ("Weathering the Unexpected" [2012])
There is little to test about the introduction of a hard fault, but the service resumption in the other DC is full of data to analyze. Also, in such a setup, getting the fault location running again is not on a hard clock, since it is about restoring redundancy instead of the service.