Halftimes of Sunday-afternoon NFL games on both CBS and Fox are split into two major segments: "Scores and Highlights", and a taped feature. Each runs aproximately four to five minutes (without commercials).
This is what I think how the networks handle halftimes of regional NFL telecasts:
By restricting the "Scores and Highlights" to half of the halftime period, the network (CBS in New York; Fox in Los Angeles) can somewhat coordinate the times where feeds of each regional game are switched back to the studio for halftime, and alert producers at game venues how long the telecast remains at the stadium before the studio halftime show.
As an example: If CBS has three 1:05 P.M. (ET) games, New York Jets at New England; Denver at Miami, and Kansas City at Washington, it could be that the games in Foxboro and Miami both hit halftime at 2:15 P.M. ET, but the game in Washington may hit halftime at 2:22 ET. The studio decides to have the halftime show for the games in Foxboro and Miami begin at 2:17, while the "Scores and Highlights" for the game in Washington would start at 2:24.
CBS studio producers could tell the announcers in Foxboro and Miami to "fill" for less than a minute and then go to the commercial break at 2:16. At 2:18, the studio halftime show begins for the games in Foxboro and Miami. At 2:22, the game in Washington hits halftime. The announcers in Washington would be told to go to a station break ASAP. At 2:23, the "Scores and Highlights" segment for the games in Foxboro and Miami ends, but one minute later, Jim Nantz et. al. begin another segment for the game in Washington.
If halftimes of two or three regional games are two or three minutes apart, announcers at some game venues may be told to chat about the game for a couple of minutes, then go to a station break. The idea is that the station breaks would occur at the same time, and the "Scores and Highlights" part of halftime on those two or three games could start at the same time.
Depening on when the halftimes of the various regional games occur, the studio team often does two or three separate "Scores and Highlights" segments for both a 1:05 P.M. (ET) and a 4:15 P.M. (ET) "window".
The studio team is usually alerted if a particular "Scores and Highlights" segment is being shown in only regional game, so as an example, Fox's James Brown could say "In the game you're watching, Philadelphia and Green Bay are tied at 17...."
But with digital technology, it may even become possible for a "Scores and Highlights" segment to run live on the first regional game to his halftime and on a delay on some other regional games, provided the delay is no more than about a minute or two. Otherwise, you'd still need to do multiple "Scores and Highlights" for regional NFL telecasts.