Still not sure what you do in an overbuilding scenario. Those poles have physical restrictions such as weight and volume. You can't have 10 different telcos serve a neighborhood: there would just be too much gear on the pole. So how do you decide who gets the space on the poles? The sensible argument says you put them up for bid in an auction, but then the incumbents still have a huge sunk cost advantage.

You spin out the vertical. If the consumers can support ten services, then those services should be able to support one infrastructure provider investing in better/stronger poles.

There would be an initial land rush if the poles were to be opened, and a large number of providers would likely fail sometime after that as the market shakes things out. Even if the market will converge on 3 or 4 providers, there may be initial demand for pole access by 10+ providers. Assuming the physical limitations on the poles are less than the demand, how should a regulatory body decide which providers get access and which ones don't?

In the end, any shared infrastructure problem inevitably ends up with a limited franchise framework because it's the most efficient way to do it. The FCC has tried regulating through this framework for years via spectrum auctions, and all they've really done is provide a form of tax revenue from the big telecoms to the FCC. The spectrum is often sold with restrictions that are eventually waived quietly if the winners hold them for a little while, and they get sold to the big national players anyway.