Earlier quoted context omitted.
The parts of SV that have buried their power lines, probably haven't gotten a whole lot of new cable/fiber/DSL than whatever was there when they buried it. SV is the perfect place to not bury infrastructure. There's no weather to worry about, and mostly people aren't going to shoot down the fiber to try to claim scrap metals.
I live in one of the few cities in the Bay Area where everything is buried, and it's refreshing not to have stuff hanging all over the place and blocking the view. Now, granted, AT&T fiber is slow to come here, but it's hard to know if the fact that the infrastructure is buried is the main reason. They are in some areas of town but not others. You can bury conduits, by the way, and not cables or fiber directly. This…
When I used to work in the telecom industry, burying conduit or cable in the ground was anywhere from 3x (bury in some dirt on the side of a county highway) to 20x (directional drilling in a heavily populated city where there's utilities all over the place) the cost per foot compared to hanging it aerially from a labor standpoint.
However, as you correctly point out, there may be restrictions on what you can hang on the poles and where, and oftentimes you'll find poles where it turns out it never should have had the number of attachments it did, but guess who gets to foot a large part of that bill if they want on?
But even then, I've seen absurd lengths gone to in the name of not digging. On Martha's Vineyard, I believe they wound up using a super-special Self-Supporting fiber that could be hung in or near the Power area of a Pole. Yes, that requires a far more trained/well paid worker than normal aerial work. Also, in that region, NESC 250C/D comes into play which makes it even more of a PITA. But it still was far cheaper than putting cable in the ground.
I wonder whether Teraspan or other Vertical Directed Conduit would be a good fit for the bay area (Saw-cut a minimal depth in the street, just lay in a special zip-up conduit for fiber or twisted pair.) If the weather doesn't tend towards large temperature shifts it works well.
Speaking of which, a couple drawbacks worth noting for buried conduit; You have to go out and do your markings, or pay someone to do them for you when a dig request is made, and you have to be ready to handle the repair when someone inevitably forgets to call or the markings are done incorrectly.