Incorrect.

B52s have the lift capacity to carry up to three of these babies. It can be easily modified to carry it. As a matter of fact, they have studied the possibility of it. It's doable. The B1 was studied, too. It's feasible.

B1 can carry two of them.
B2 can carry one.

MOAB: 22600 lbs
B52: 70000 lbs weapons lift capacity

The likely candidate is the use of the MOP: massive ordinance penetrator. This baby is 30000lbs. It is designed to penetrate very deep bunkers. The B2 has been modified to carry two of them.

http://www.defenseindustrydaily.com/mopping-up-the-usas-30000-pound-bomb-03172/