The justification is that there's a particularly high density and quantity of wiring around that fire station (one of two for LAH, IIRC) and that Moody is a major access route for emergency services and evacuation. A giant bundle of wires coming down across the road would strangle a response.

A simplistic napkin math computation says that the cost delta in electricity between what Santa Clara pays and what PG&E customers pay, times the amount of electricity that LAH residents consume would pay for the entire undergrounding in 5-6 years.

So to my mind, it seems like a simple argument in favor of a municipal power utility that charges PG&E rates until it pays off its infrastructure, and then charges a more reasonable rate thereafter. Of course this assumes that LAH could achieve Santa Clara levels of cost efficiency, but it doesn't seem crazy either.