One shared network, separate companies in other ways. Building four networks when one will do the job is an unnatural act, FCC Chair Tom Wheeler reminded CTIA. He pointed to the effective joint build of Cingular & T-Mobile more than a decade ago. For 5G high-band, he sees little choice. Highband has short reach so needs many cells - easily a million to cover most of the U.S., compared to the 50,000-70,000 cells AT&T and Verizon now have. The 4-7 networks necessary for competition to work well are not going to happen. Vectored DSL also is unlikely to be shared; that means the end of network "unbundling" in Germany, Italy, England, much of Poland and some of the U.S.
Competition can survive a monopoly in the home connection if it is strengthened in other parts of the network. Wheeler is on target with, "We ought to explore creative options on how best to build that infrastructure. ... We have to learn from experience and get in front of this challenge."
There are choices other than strong regulation of a monopoly or duopoly.