In practice I have no clue how it works out though.
There are no rich shareholders to foist the costs on. No investors are going to pay tens of billions of dollars, more profit than PG&E generated over several decades, to pay for 10% of the electric wires to be buried. If there were any investors on the hook for this, they would simply declare bankruptcy and walk away.
The only option here is that the costs are paid by ratepayers, or taxpayers. There is no other option available.
IMHO an infrastructure of this size & importance might just as well be state owned, but I guess rate hikes will also do. As long as there is some mechanism to help (yes, probably with tax money) those who might not be able to afford them...
It's far from perfect, but actually-public utilities are responsible for a lot of disasters too. It's not obvious that nationalizing PG&E would be good for anyone.
CA has some of the most expensive electricity in the nation. So it doesn't seem like the idea worked out.
In PG&E's defense, it's not literally cost-plus, and the CPUC doesn't always rubber stamp everything. Imagining the government alternative, what would really be different? There will still be a big bureaucratic organization full of imperfect humans with muddy incentives and limited resources. Would PG&E be better if the board of directors was appointed by politicians instead of elected by shareholders? I doubt it.
PG&E has to get approval for their spend from the PUC and for any rate hikes.