For the past 10+ years there has always been an 12:30pm Saturday game each week. The selection process went like this: 1) CBS got first pick (usually the best game of the week) and airs the game at 3:30. 2) ESPN comes in and selects various games and airs them on their family of networks (ESPN, ESPNU, ESPN2, etc.). 3) Lincoln Financial (used to be Jefferson Pilot) came in and picked a game. This game was the 12:30 game. 4) If a school didn't have their game picked up, they had the option of producing it themselves and airing it PPV. 5) If the school opted not to produce a PPV game, ESPN had to pick up the game.
As far as programming: ESPN is contractually obligated to air 450 linear events including 45 football games (3 games every Saturday during the 15 week regular season) and 550 digital events.