Sounds like this wasn't caused by power surges reaching the equipment but rather an effect of repeated power loss to drive arrays not fully designed to handle it. The article is pretty unclear. Still sounds like an infrastructure problem though.
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I think the reference to batteries would more likely be in reference to a DRUPS (Diesel Rotary UPS) which most datacenters run, sometimes with some form of battery in combination with the flywheel. Typically the combination of kinetic energy in the flywheel (and potentially batteries) only hold enough power to last for 30 seconds or so (often as low as 10 seconds), which gives the diesel power generators enough time to come online and take over from there.
What I guess is that might have happened is that grid power was lost, they switched over to UPS fine the first time, grid power came back so they swapped back, repeat a few times and on one of those times the batteries didn't have enough charge to keep things going for the generator swap-over.
At BT they where tested every day for the really sensitive systems.