For example, CBS is buying the right of use to air a game with B1G schools at 3:30EST. It essentially purchased a priority pick preference for the slot.
Remember, the networks don’t own the actual IP of the schools in the conference; they own the right to use that IP at a certain time. They generally pay based on the number of quality matchups available for them to select from. As long as Fox, CBS, and NBC get the content they want at the time they want they are satisfied. I admit the contracts may vary and networks may purchase exclusive rights to a conference’s entire TV inventory regardless of whether a game is aired (see SEC and ACC arrangement with ESPN); but this is typically less likely when multiple partners are involved. As long as the B1G provides the quality of content desired I imagine the networks are fine. The problem with OOC games is sometimes the content sucks (games against MAC schools) or the conference’s TV partners only get access to one of the games in the series (the home game).
Having 10 games with the addition of four schools creates the possibility of more intriguing matchups and keeps all the game inventory in conference.