Ban comes into play when Pokemon initially bought down in a lower tier was deemed too intolerable in that environment through suspect testing. These monsters would not be allowed in the lower tier (they got banned), yet they are not exactly 'qualified' to be in the higher tier (due to their low usage in the higher tier). So they are in a tier between the two tiers (ie BL).
Unless BL battles start picking up (I don't think anyone wants to use Kyurem against UU pokes that badly) then competitively speaking banned pokemon are essentially forced into a higher "usage tier." Therefore, banning (by nature) has a direct effect on a pokemon's tiering in the context of actual use in the competitive metagame. I meant to point out that banning is simply a method of tiering pokemon based on what tiers they're to good for. In conclusion, banning/tiering are two sides of what is basically the same thing.