In alt.home.repair, on Wed, 29 Apr 2020 05:44:18 -0700 (PDT), TimR
wrote:

On Tuesday, April 28, 2020 at 4:36:29 PM UTC-4, wrote:
I was here watching them do the one near my house. They just drive the
guardrail metal down with a power hammer and strap it to the pole.
Then nail on the cap. The whole process took less than a half hour.
These guys probably do 10 or more a day. It took them almost as long
to do the surveys to see which poles needed it. They had to dig and do
some physical testing of the wood for that. The guy said they only
look at the first foot or two because that is where the problem is. A
few feet down the poles are solid.

Walking the dog yesterday, we heard a woodpecker hammering away and it had to be on a telephone pole, but I had trouble spotting it. Finally with some help we saw it. It was at the very top of a pole, and it had excavated far enough in that only its tail feathers showed. The power company had already set a new pole next to it, just hadn't transferred the wires yet, so they knew how bad the pole was. But if they rot from the bottom up, that one had to be pretty bad.

The pdf file listed in this thread had a section on woodpecker repair,
with a drawing or two.