In Europe, most countries have a reasonable solution: The incumbent telco in most countries have been required to separate out the business unit that owns and operates the cable sufficiently that it can be accounted for separately.

This business is then generally required to provide equal access to anyone on a "cost plus" basis exactly because the cost and complexity of laying new cable is considered a massive barrier to competition, and besides we don't want a ton of companies digging up the street all the time or erecting new poles.

E.g. in the UK, the "last mile" of all landlines installed by BT are now handled by BT OpenReach. Consumers can call their preferred ISP or phone provider and ask them to take over the provision of services on the line, and the ISP deals with BT once you've authenticated the request.

The service is then either provided via backhaul over BT's network - that is, the ISP provides a few central nodes where they interface with BT, and hands over a raw data stream from each subscriber at those points - or the ISPs pay (on a cost regulated basis) to put equipment in BT's echanges. The latter has the advantage that they can offer services BT can't/won't and that ISPs that depend on backhaul from BT can't - some ISPs beat BT in certain areas this way.

It's not perfect - it's limited by BT's upgrade/buildout schedule, but BT does face competitive pressure from Virgin (cable provider), and also does face the possibility that someone will able to get finance together to lay cable to compete if they don't watch out, though the latter is less likely.

But beyond the last mile, there's fierce competition.