Here is some information on Sunday "bonus coverage":
When a media market's regionally televised game ends before the others, the network (CBS or Fox) may switch to "bonus coverage" of the ending of another game. However, the league imposes two restrictions that are designed to maximize the ratings of the late games on the doubleheader network, which tend to record the most NFL viewers during the day, often beating the audience for Sunday night games.
First, bonus coverage offered after any early time slot games cannot be shown past the start of the late time slot (either 4:20 ET for the doubleheader network or 4:25 ET for the non-doubleheader network). This prevents people from continuing to watch the bonus coverage instead of seeing the beginning of the late doubleheader network's game (which is usually either their local team or the network's featured game). Again, the networks may show highlights of the game, and usually will at the earliest opportunity. The network broadcasting the single game will sometimes show each play as soon as it ends as part of its post-game show. A station originally getting the game featured during bonus coverage will stay with it unless they are leaving to show a local team.
Second, bonus coverage cannot be shown after a late game on the single-game network because it will run in opposition to the ending of the late doubleheader network's game(s) and NBC's pre-game show. However, the single-game network usually schedules most of its top games in the early 1:00 ET time slot (except for west coast teams' home games, and possibly either a Giants or Jets game), so this does not tend to be a major issue.
If the doubleheader network's games all finish before 7:30 ET, it is supposed to conclude the post-game show within 10 minutes to protect NBC's pre-game show. If any games finish after 7:30, the post-game program can run until 8:00 ET. However, this restriction seems to apply to game footage only; on several occasions Fox has run its post-game offering to 8:00, despite all games ending before 7:30, by airing only panel discussions and interviews in the latter portion of the show. On the other hand, CBS rarely airs any post-game show after its doubleheaders or 4:05 single-games. This is because 60 Minutes is one of its signature shows, and CBS makes every effort to start it as close to 7:00 or 7:30—its traditional airtime—as possible.
This does not appear to restrict CBS or FOX from providing bonus coverage on as many games as they elect to.