Even if they go into bankruptcy (Chapter 11, say) they are legally allowed to recoup the costs of this as part of being a regulated utility, so I would expect higher utility rates to customers as a start for the next few years in order to either pay for the liability insurance or (less likely) to bring their infrastructure to a court-arguable higher standard so as to avoid accusations of liability in the future.

That said, as a private citizen I don't see how a person starting a fire accidentally (not sure how you prove malice if a transformer fails?) could be held liable for all the property damage further downstream. That's what private insurance is for.