There are a lot of differences between the telco industry and anyone else. For example, a telco provider is required by Federal law to maintain service on an essentially "no matter what" basis, and so therefore they have massive equipment redundancy. Double, triple, and quadruple redundancy is fairly typical in that industry. In Orlando there is an AT&T telco facility that's double-walled, brick exterior, and the big access entry ways into the building are normally kept bricked up and over, and then that section of the wall is disassembled, the massive entry doors opened, access is granted, and then after the fact everything is closed up and bricked up again. At this point, the building is largely empty because it was designed to warehouse telco equipment of a different era, and modern equipment, even highly redundant, takes up a fraction of the space.
Now, take a look at how your local cable company, which offers VoIP-style telco, varies. There is no such equivalent redundancy requirement. They don't have to necessarily deliver a certain minimum-quality service to your home. They can have all kinds of outages. Cell carriers are in largely the same boat as cable VoIP providers. If they had to provide an equivalent amount of redundancy, who knows how large all of our cell bills would be.
Now, as far as monopoly and oligopoly are concerned, let's consider that the cellular industry started out as a fairly capitalist "invisible hand" style marketplace, and it's still somewhat like that. However, there are far fewer national carriers today, and so it is much closer to being an oligopoly. Typically your physical utility services -- telco, power, cable -- are geographical monopolies. In many cases there is nothing devious behind it; it simply is what it is. However, in other cases (and I'm thinking telco and cable) it is no longer a completely legitimate geog. monopoly. Rather, it is a contractual monopoly; that is, other providers could come into an area, but existing ones have signed exclusive-deal type contracts with counties / cities to be the only one available. This is part of the reason that, traditionally, satellite t.v. providers have been so popular.