Nertz! said:
How does that work with the must carry regulations?
Must carry favors the in-market broadcasters. Once they demand carriage in the market, it must happen. Which is why some markets have a glut of shopping, infomercial and preacher channels that are a waste of space. But, if they demand to be carried (and are a full-powered signal, LPTV stations and PBS don't count) then cable within the market must pick them up. The broadcasters make deals with each cable outfil in their market(s) and sometimes a number of markets are negotiated at once.
However, broadcasters also have the right to demand compensation for carriage. That can be in the form of a charge per subscriber, the carriage of a co-owned cable network (think MSNBC and CNBC when NBC O&Os are negotiated), or all of the above.
If they do this, and no deal is met, then they can be removed from the cable company's lineup. 'Crap' channels know better than to do this (they just want to be on), but the owners of big 4 network stations have the leverage to make all sorts of deals across multiple markets. To my knowledge, viewer outcry always favors the broadcasters and, though there have been some well-publicised network blackouts on cable - none have lasted.
One more thing - network affiliates generally have exclusivity rights within their individual markets. There are exceptions to this for "significantly viewed" out of market signals and others, but for the most part they have exclusivity. Thus, the station owners usually hold all the cards and they know it.
That's the Reader's Digest version, though I'm sure that some folks here can be more exact about these terms than I have been able to be.