I think technically CPUC approves at least a subset of expenditures, but yes there's the weird incentive where wasting money can actually increase profits
All the CPUC rate setting committee discussion minutes are public. You can look up what is discussed.
The regulator gets down to relatively minor capital investments like fence replacement at substations.
If the government has to approve expenditures and profit margins, there seems to be little reason for a private utility to exist?