I know we are talking about CBS, but Knoxville has been a top 10 market for ESPN for years. I don't really see how either of the Mississippi schools offer a better viewing market than UT. Mississippi State and Vandy certainly doesn't. When you take Alabama, Georgia, Florida, and LSU out of the equation, it's pretty clear to me. But I don't really know the numbers.
It's pretty got to do with several things, though. It's not just college market size. How the teams in question are record wise on the season, how big a viewership/fanbase size the schools offer, rankings/national standing, star power, and so on.
If Miss St is still number 1 and still playing to try to earn a spot in the conference championship game, they'll gladly give it some heavier consideration, especially with a national star /heisman candidate on the team like Prescott. (personally, I think it's more likely between that one in such a scenario and - if it's still ranked - Ole Miss v Arkansas...with favor maybe going slightly more to the latter).
They've also in the past shown they're fine showing a highly ranked team (that's also in competition for the conference championship) against the worst team in the conference. They did it in 2001 with #7 UT playing Vanderbilt. They've done it with Alabama and Auburn before as well.
(I'm not saying by any means that Knoxville isn't a major or more productive market than that of the two Miss schools; I'm saying that of the Miss schools and their fan bases is big enough that - when the two are doing/performing as well as they are this season - it's good enough of one for CBS to feel okay/comfortable going with it, rather than hesitant.)
Late in the season, "intriguing" can equal more viewers because Florida and Georgia fans will tune in to see how Mizzou plays because the East is on the line. JMO.
That's the thing though. A broadcasting company isn't going to make a decision based off of "some fans might flip over out of curiosity." That would only be a partial amount of a fanbase and at best it's an uncertain fraction at that. That's not really a strong selling point (both still also play that day, do they not?). Those aren't guaranteed eyeballs, nor would they be near the regular fanbase's size/amount.
Especially when you've got a situation like CBS has with Missouri; the 2 Missouri games they actually, actively selected in 2012 were two of the three lowest rated games CBS has aired in that time slot in the past 10 years (granted Missouri was bad that year and they were blowout games against Alabama and South Carolina). It showed the next season when while Missouri was high in the rankings and leading the East, their games were avoided or passed on until the SEC Championship (the game that network had to show them in...some of their matchups against ranked teams before then even got passed up for matchups between bigger name, unranked teams).
With UT not being ranked either and just being a 5 win team, it really doesn't add/create enough to really make that game more favorable for a nationally televised game.
Granted, again, I could still possibly be incorrect regarding this.