One question I often get is can local or state governments require mobile carriers to share cell sites, particularly small ones that can be attached to something like a street light pole?
There are technical issues with carriers sharing big, macro site towers, but those are generally solvable if the tower is big enough, and cities can sometimes pressure or cajole carriers to work together. A major consideration is whether the location of a given tower meets the engineering requirements of a mobile carrier. Carriers have different strategies for designing coverage patterns, based on a number of factors, including their perception of where their customers are, what their customers want and, particularly, the frequency bands they’re using. Different bands have different capacities for carrying data, different effective distances and differing abilities to penetrate through obstacles like building walls, dense foliage or, in the case of new, millimeter wave frequencies, even moisture in the air.
Small cell facilities are another ball game, though. The basic idea behind small cells, whether it’s for 4G or 5G, is to put a low-power facility closer to users (i.e. at street light/utility pole height), so that spectrum (including finicky millimeter wave bands) can be reused over a large area, and so mobile carriers can target particular groups of customers and/or fill gaps. That leads to tighter design parameters, which mean less flexibility for shifting things around.
Then there’s the question of how to share a pole. Even if it’s physically possible, adding a second set of antennas and electronic equipment to a pole will only add to the visual clutter that local governments try to avoid. Theoretically, sharing antennas or electronics might be possible in some cases, but even then it’s almost always impractical.
Policy is also a huge hurdle. The Federal Communications Commission and the Communications Act make it difficult for states to get involved in mobile carriers’ engineering and coverage design decisions. Probably not as difficult as the current FCC would like to make it, but a key question is whether a state’s rules "prohibit or effectively prohibit” deployment of telecommunications services.
The (for now) republican majority on the FCC seems to think that any state or local attempt to meddle in the affairs of mobile carriers like AT&T or Verizon rises to the level of an effective prohibition. Federal judges are in the process of deciding whether the FCC’s power in that regard is absolute, but there’s no realistic prospect of them opening the door wide enough to allow states or cities the degree of technical design regulatory authority that would be needed to require mobile carriers to share facilities.