So I'm an across the board wildlife supporter. I recently noticed on my daily bike rides, a woodpecker "nest" in a HV utility powerline out in the country that only feeds the municipality's two main water supply wells. There were two woodpeckers last time I saw it, one inside looking out, the other inches away. The nest is under the powerlines, about 2/3 way up the pole. It's a treated fairly new pole. The nest has to weaken the pole. How much, since I have no idea how large the internal cavity is. There is not visible pole ID tag I saw as I rode. by. If pole collapsed in a hurricane, local water plant would be on generators. I have reported similar concerns in the past, and usually get steered in a circle, and its a future concern not immediate, typical bureaucracy run around.

So the main question, does an occupied woodpecker nest compromise a HV important utility pole?

interesting question, although i have no idea if the pole would be compromised or not.
does the pole have any obvious knots or other defects that would compromise the pole strength ?

Waste of time.. those poles are inspected on a regular bases and they may know about it already

You should see how many nests are in a 345KV I just inspected. As long as they don't touch the ground, they're fine. If they do touch ground, someone will be making some overtime.

As a lineman for 40 years I can tell you there are poles everywhere that woodpeckers have made nests in. (yellow jacket nests are worse) You couldn't stop it if you tried. Also I can tell you we don't inspect poles on a regular basis not enough time in the day to do that. Only when we are working in or upgrading an area. Kinda like a lady that was upset because we didn't know her street light was out for 2 weeks until she called us. Thought we should be able to keep track of every light in town without being called. Lol! The first time I saw a ton of woodpecker damage was in southern Illinois after their inland hurricane. Brand new high line with holes everywhere. Their fix was they filled the holes with expandable foam.

To answer the OP's question, yeah...the bird hole will weaken the pole somewhat. It will only matter if the line falls on 1 side or the other of the pole with the bird hole. When the weight of the wire on the opposite side pulls everything in that direction, the bird hole pole snaps like a twig! Then...second 70 and I will get paid triple double overtime and a half to go fix it! Just kidding.....we're both too damn old to be doing transmission work! I've been doing line work for 42 years. I worked transmission for 3 years in the mid 80's, and when we had peckerwood nests, we would nail bird wire over the hole. It worked so well that the wood peckers would move to another pole and beat a hole in it! Next time you go by the pole, stop and take a pic and e mail it to your power company with an address. They will go look at it and determine how critical it is. I think the OP lives in FL? If the pole belongs to Dook Energy......don't look for it to get replaced anytime soon!

You should use your excellent skills and construct them a habitat that you can move that and them into your home for year round enjoyment.

If you don't tell them they can't take action, can they
I've seen joint local power and telephone poles so full of holes I wouldn't climb them, I had to get a bucket truck to work on that terminal that day.
It took a little over 30 days for our engineers and construction dept. to change it out back in the late 1990s, BTW our company didn't have pole inspectors, they relied on the employees to take action on bad poles
I use my pellet gun on woodpeckers on my house, I have over 40 trees on the property here that they can feed and nest in with out me taking them out
There good as long as their not pecking holes in my wood sided house

Around our property we have nesting pileated wood-peckers (large prehistoric"woody woodpecker" looking things). If the lines are in a straight alignment the wood fibers of the pole will do a pretty good job of keeping things up as the size is about 200% of what's needed. The wood pecker hole only uses about 15 to 20% of the cross section of the pole and really does not pose a problem. Problems occur after several years of nesting use, it stats rotting from the inside out. Now, if it's a guyed pole or has a transformer or drop to a house there could be some strain that as above the power company monitors.
Here we have several snags and a couple power poles that have nesting cavities. The little acorn type birds don't seem to nest in the poles, rather they jamb acorns in cracks to save for when the bugs inside get large and they return to eat them.
The power company was replacing poles and I caught the guys at lunch and asked them about the nesting birds. I asked if they were going to work around the nest and they explained they install the new pole adjacent and top the old pole off below the cross arms and above the nest. They retrieved the old pole a couple months later when the birds fledged.The people doing the work said they have biologists and know they have to protect the nests.
The land owner where the nesting occurs (and the poles were located) is a good steward and leaves a few good sized snags as wildlife trees for the birds use. Even with that sometimes they use the few power poles in the area for some reason.
idk what kind wood peckers you have, but here, pileated are considered keystone habitat modifier and are a protected species. Pileated iirc are the only that create the large hollows in trees out west.

I bumped into the wife of a local FPL lineman, and mentioned the situation to her, way outside her expertise, but she quickly mentioned, Florida Power & Light will quickly replace the pole. which stands to reason, since I can't ever remember a pole in my region of Florida with a Woopecker nest. Being they are currently doing line/pole upgrades in the area for the next 4? years that she shared, I marked the pole today with flagging tape, and will at least report it, being we are days away from Hurricane season, and its the only feed to the local municipality's city water wells.

I'll name the relocated woodpeckers Mr & Mrs Potatohead.

^^^^^^^^^^ Now that there is funny!!