Aren't customers on the hook regardless? PG&E gets it's money from customers, which would imply that customers are paying would be the ones to pay down the debt. Maybe they mean customers are a captive audience, and rates could be raised to cover the costs of the debt without impacting PG&E's profits.
But a drastic expense can cause bankruptcy, taking ownership from the stockholders and cause a resale bellow book value to new risk takers that now factor in this kind of risk, pressure the new management to avoid it repeating, and are more or less happy with current rates given their lower investment.
Watch them cast that as an injustice that our corporate social net needs to prevent instead of the correct result.
Giving them a sweet bond deal essentially gives them the opportunity to turn it into longterm price hikes and reward current shareholders for owning a fire hazard (or really not claw back that reward by killing the stock price as it has already been paid out in years of higher dividends due to lower safety costs.)
If infrastructure/natural monopolies are run by the state, that is a decent solution so long as people are elected into power that understand they're making decisions to maximize the benefit of the citizens.
What is needed is tighter enforcement or a framework which incentivizes entities for innovating ways to improve services to their customers and minimize societial impact. While bankruptcy and the bond market is a decent check on that behavior, those who enacted those policies and made more profit with them enriched themselves and simply had the clock run out on their corner cutting not causing external damage (externalities on society). It doesn't prevent that behavior but it does prevent it from continuing.. for some time until the new board looks for ways to further their return on investment. Which eventually leads to the similar damaging behavior.