I don't know exactly how it works this year between BTN and ESPN, but ESPN gets to pick a bunch of games each week (exceptions being the night games that were decided at the beginning of the year and whatever other rules BTN has) and then assigns the games to whatever network they want/whatever timeslot they want from there. That includes ABC, ESPN, ESPN2, ESPNU and ESPNEWS.
That's entirely decided by the network execs and what they think will draw more eyeballs, and how they decide to spread out the eyeballs throughout the day across their properties. In the case of Oct. 8, they felt they could attract more viewers with BYU-Michigan State and/or Indiana-Ohio State at the 2:30 timeslot than Iowa-Minnesota.
That will change next year with Fox entering the fray, some weeks Fox will get first choice of games, some weeks ESPN. And then it'll alternate (one week Fox gets first pick, next week ESPN). It'll also mean fewer games on ESPNU and ESPNEWS, more games on FS1.