You're both talking apples and oranges. If the BCS controls only one bowl, it is unlikely that the BCS will have any antitrust issues, particularly is it is made up of every football conference.
So no, in the proposed system, the BCS doesn't do anything anti-competitive. But that is not to say that the behavior of the conferences and individual bowls in the proposed system is immune from antitrust concerns. If the Rose Bowl freezes out all but the Pac 10 and Big Ten, and refuses to consider others, how is that not collusion at some level? You'd need to look at the market. In the market for bowl games and bowl game participants, the bowl tie-ins reduce competition. The Rose may say they're not going to big big bucks to get LSU, as long as the Fiesta doesn't try to steal Oregon. Dividing up the market with your competitors is illegal. Is it a slam dunk? No. But it's a colorable claim.