5-10 sure what about 20 50 100? Wait till you see their crews actively sabotaging each other, hell I see it with AT&T phone vs fios since one in union and views the others as scabs. I assume you have never been to someplace where there are many last mile networks in competition it's pretty ugly but aesthetically and functionally.
A last mile monopoly, no different than water or sewer. I'm only talking about last mile not transit, ISP's simply colo some gear in the CO or pop a bundle of fiber to their own location. Were talking about literally only glass and channel allocation nothing that needs power etc etc etc. The ITU defines 18 channels for CDWM though 8 or 16 are normally used. Security wise mandating macsec is pretty trivial. That is about 25gbs per channel with today's tech. At the end of the day muni's do monopolies well in a cost effective manner.