I would be very leery of a datacenter that didn't have their own on-site generation plants that can be guaranteed to supply power in the event of a grid failure. If a substation goes down on a cloudy day, I would hope that they have a big diesel generator or gas plant on standby regardless.
The solution to that is to have enough solar to generate the power you need even on cloudy days, then sell the excess to the power company on normal days.
