I don't see an 1 loss SEC team getting in over an unbeaten Oregon or Big 12 team. They'd definitely get in over those teams if those teams also had 1 loss.
But if they're unbeaten they'd be ahead of the SEC team in the human polls, and probably in the computer part of the BCS too as they'd all have pretty tough schedules. I mean 6 out of 10 Big 12 teams are ranked in the Coach's poll currently.
Just no way unbeaten major conference teams get left out in favor of 1 loss teams. With equal records the SEC champ definitely gets in most years (though Auburn did get left out in 2004). But the bias isn't such that they'd get in over unbeaten Pac 10/Big 12 champs.
I'm not saying I like it, but if a 1-loss Florida or South Carolina beats #1 Alabama (who remains undefeated at that point) in the SEC Championship game I guarantee you will hear all the talking heads go on an on about "the SEC gauntlet" and the poll voters will eat it all up.
Have you forgotten last year already? A 1-loss Big 12 team was snubbed in favor of a 1-loss SEC team, a 1-loss SEC team that already lost to the other team who was going to the national title game. Let's not pretend that an undefeated Pac-12 and Big-12 team will suddenly make the SEC favoritism, which they've earned, go away.
My guess is that the Pac-12 team would get the shaft, since beating USC twice doesn't look as impressive as it would have for Oregon and Oregon State just wouldn't get as much love in the polls.