Bunker busters are armored at the front. They absolutely would not care about ERA.

However if you were to have a sizable layer of Jell-O between the outside bunker armor and the inner bunker, it could slow the bomb down, with the main charge detonating away from the inner bunker armor. The blast would be further mitigated by the afore mentioned Jell-O. It would also make the post-blast analysis delicious.