The definition of Monopoly really comes from that 6th company attempting to enter the market:
1. No legal/physical means to provide service in said jusirdiction: Monopoly
2. Not financially feasible entering said market leaving a few dominant players to fight over market share: Ologopoly (this can happen with anything as long as competition exists, this should eventually reach saturation in price conscious markets)
3. Simple boundaries for entry, and good rate of return: Open competition mode, that should arguably not last exceedingly long as continually entering competitors race in and lower prices to entice more business
For Sweden, the stiff steep fixed costs of entry have been largely paid and continually subsidized by government maintainance, which gives a natural benefit to players entering the market in avoiding large capital outlays. This doesn't mean the system is 'bad' or inefficient, or even taking cash from tax payers. They -could- be revenue positive for all we know as many gov corps are, so don't give me that song that all government is somehow intrinsically wasteful (or a bunch of robbers). It just shows your political leanings, not your common sense.
Since the cost of entering the market requires comparitively little vs. an American incumbant, they can and most likely do discount their rates against one another to maintain their position. Its very possible but I couldn't be sure that the gov actually sets pricing guidelines, but for that I wouldn't know. So no, the Comcasts of Sweeden aren't making stupidly large profits, but I'm sure they're in the market because there's enough room to make a desired profit point. Think of it like the days of dial-up. In those days, anyone could be an ISP with a few lines and a bigger pipe paid to an ILEC (or some other provider) and you could get by. You would grow if you had a good service offering beyond just the physical medium (which was by and large the same besides over-saturation).