Sure. If there was gross negligence, some liability would be reasonable. Probably not 100% of damages, but some. That’s not what we are talking about though. I think under current law they could be liable even if they took all due care.
PG&E bills literally include a line item for maintenance, beyond the basic costs. PG&E has repeatedly issued bonuses and comp packages funded by cash they received from that line item while not performing maintenance of their network.
This is exactly what happened last year (line that they weren't maintaining caused that fire), and when they blew up san bruno (when a gas line that had even been stated to need maintenance exploded and killed people).
If you can make a profit while doing all the required work, then fair play to you, but if you're turning a "profit" without performing all the maintenance your network requires, and then getting tax payer support whenever that goes wrong you are not running at a profit. You're a tax payer subsidized siphon, taking money from tax payers to fund bonuses and investors. If you can't run a profit without tax payer backup, you aren't profitable.