I don’t know — just imagine how many places the mains power is tied into all of the buildings. Each of those places would also need a mains cutoff, and they would need to all be thrown/active at the same time before the cogen plant could be activated independently. At a place the size of UC Berkeley, that would be a pretty big cost (and logistical nightmare).

If the system wasn’t designed for the switchover from the beginning, I can see how it would be considered impossible/not practical to do. Especially when this type of “blackout” was thought to be rare.

I’m sure the prior assumptions would be reconsidered today.

> just imagine how many places the mains power is tied into all of the buildings

Not many? As in, I don't think many buildings would have two separate power feeds. I'd expect a small number of very large connections from the cogen plant and the outside word into local distribution network(s), and then everything is single-path from there on.