Well, since the traditional behaviour of telecoms is that, once they've eliminated the competition,
I cannot speak to Canadian regulations, but down in the US it would be very hard for one wireless carrier to "wipe out the competition", since the FCC auctions for wireless bandwidth were specifically set up so that there were two winners for each service area. It was a design goal that there be competition.
To also address your point about the users of the unlimited service being sad, their unlimited service was effectively a (substantial) discount, subsidised by every other user of the same common infrastructure.
No, it was that they were actually costing less to the telecom so they paid less for the service. It's irrelevant if they were subsidized or not, the point was that they're going to be unhappy. I don't know too many people who would say "gee, I now have a data cap on the streaming video feeds that used to be unlimited, but that's ok because I was leeching off of everyone else..." They're going to think "thanks Canadian regulators for screwing up my service and making me pay more."
That was in effect very much a parallel to abusing monopoly power in market to obtain monopoly power in another,
Cell phone service is hardly a monopoly in any sense of the word, neither is streaming video service. What it actually was was a company saying "I can provide this to you cheaper because of vertical integration". Vertical integration is how many companies cut costs, and it doesn't create a monopoly.
Because the service cost difference in entertainment media is negligible.
While the cost for the actual content may have little difference, the cost of transport isn't the same by any means. You need to look at total costs, not just the cost to buy a program package.
What the telcos were doing was subsidising the bandwidth cost of their media content users and spreading the cost to all their other users, who often didn't have alternative ISP choices.
Well then, Canadian regulators screwed their constituents pretty bad, because in the US there are alternatives. It is that way by design. AT&T, Verizon, Sprint, T-Mobile -- I believe all four are infrastructure providers -- and then the contract carriers like Cricket, USCellular. The list of the latter is nearly endless. You don't like one, you've got another choice. Too bad Canada's equivalent to the FCC didn't think ahead.
But that still doesn't mean that the unlimited users were being subsidized. They added nothing to the peering costs, so they got a better price. If you want to talk about one group subsidizing another, look to the heavy data users who expect unlimited service for the same price that the low-volume users pay. That's 180 degrees from your claim.