I'm not sure why people keep pushing this narrative about PG&E doing everything right when it was clear they did many things wrong. They've been found criminally negligent multiple times now on separate occasions.
As to whether or not their equipment caused the large fires is another issue and another discussion altogether.
The entire reason why they have to shut down their systems is because for years they've been making shit up in order to avoid having to do actual maintenance. And now rather than performing the proper safety inspections and maintenance, they're shutting down the systems due to their prior screwups.
If I remember rightly, the case which set this precedent involved a fuse correctly failing open and managing to set fire to some brush beneath the pole which had grown up in a few months since they'd cleared the entire area around it. There is no maintenance standard they could follow that would protect them from liability; all they can maybe hope to do is decrease the number of fires and the consequent costs somewhat.