Don't have a clue as to the cost but since there are homes built there, I assume that the water and sewage pipes are built under ground {lava rock}, so it can be done.
How much longer does it take to find and fix a faulted underground cable?
It doesn't take any longer to find the outage, {that is evident by lack of power to certain homes} and while it might be a little longer to fix, since they are buried, the outages are less frequent.
Are you willing to pay 10-20 times your current bill?
My electric bill is the exact same as on a usage basis, as is any local resident that has their electricity delivered by overhead wires.
How did you come up with this 10-20 times question?
You obviously have no clue, thinking outages are fixed as readily and don’t understand the costs. I’m an electrical distribution engineer for utility companies, you?