MBB won't care about Tier2 offers, this is not the competition they are concerned with. If they ask you about other applications you have, the only real question is whether you are applying / interviewing to the other MBBs, and perhaps the likes of Amazon or Google. If you do need / feel the need to mention Tier2, I think saying "plus a few Tier2, such as X, Y and Z" would be just fine.
Again - as far as MBB is concerned, they will assume you will reject any Tier2 offer right away. And if you don't, you probably should :)