There are several rules that come in to play regarding what gets televised over the local channels. Obviously there is the one about blackouts, where the game will not be televised in a 75-mile radius from the stadium if a game does not sell out; most everyone is familiar with that.
CBS and FOX will show at least one game in each market every Sunday, regardless of blackouts. And each network gets eight 'doubleheader' Sundays where they get to broadcast two games while the other network can only show one.
However sometimes a network will only be able to show one game in some markets on a Sunday even when it is their turn to have a doubleheader. The reason for this is because the NFL also has a rule that if a game does sell out, that can be the only game on TV within that same 75-mile radius.
Apparently the rule was put into place to insure people go to the stadium and spend money there rather than stay at home and watch a more compelling game on TV. The thing is that people who purchase Sunday Ticket would have a fit if they could not see their favorite team because of this rule. So the compromise is that the rule only applies to the local station and not the Ticket. I don't think it results in the original intention of getting people to go to the stadium any longer, but it does help boost business for the Sunday Ticket - whether it be at home or at a sports bar.
An example of where this comes into play for Pats fans would be in week one if you were in Chicago or Pittsburgh. Both those teams are playing an early game at home that day, which will be on FOX in those markets. Even though it is a CBS doubleheader in week one, there can be no game on CBS in Chicago or Pittsburgh while the Bears and Steelers are playing at home. Without that rule the Pats-Bengals game would probably be shown there, but it will not be aired on a local channel in those two cities.
