I would guess conventional deep penetrator bunker busters (by the nature of what they do) are pretty harden and designed to take a lot of G-forces and temperature before going boom. I think the follow ups would zoom right through the loose debris easier than the primary zoomed through a couple hundred feet of solid rock.
Yes, according to Wikipedia there are warheads that can dig pretty deep into the ground. However Iranians placed their plant even deeper - it is built under a mountain, just like the Cheyenne Mountain facility in the USA.
I think the follow ups would zoom right through the loose debris easier than the primary zoomed through a couple hundred feet of solid rock.
One common concern about that is that it's difficult to achieve precise aiming when there is so much dust in the air after the first strike. Optical targeting is impossible, and GPS may be unreliable too - besides, you have only milliseconds to react, and you need to place the follow-up bombs all within a few feet from each other.
The space shuttle bay is 15’ x 60’. I’m not sure how many 59 foot long tungsten telephone poles can be moved into orbit at one time. We’d need to develop a GPS guidance package that would survive re-entry along with a rocket assist to get the rod from God started on the way to the target. It would beat the hell out of any bunker buster bomb. The nice thing is it’s not nuclear.