MOP penetration based on openly known information and using the penetration equation would be something closer to 8 meters on decently hard rock, instead of the 60m that the media is claiming which is true but for more cooperative surfaces such as silty clay or dirt.
MOPs could very easily seal entrances and exits, vents, access tunnels etc with one or two hits. But to penetrate the facility which is estimated to be under 80-90m of rock and has a possibly further hardened shell, you would need 10 successive hits for penetration , possibly 8 successive hits to start doing internal damage (assuming the penetration ability doesn't decrease with successive hits, but I'm not sure about that - probably nobody has tried this many successive hits).
With some error probability accounted for you would need 8-10 B-2 sorties carrying 2 MOPs each to seal off the access tunnels and get a complete penetration. 6-7 Sorties if you just want to penetrate and thus don't care about sealing tunnels. 3-4 sorties if you don't want full penetration but think sealing the facility shut will be fine.
Honestly the numbers aren't too absurd, and in my opinion not out of the American reach if they really do decide to shut the facility down. In the end it would depend on their internal assessment on how effective they think MOPs will be and how much risk they're willing to digest to run these sortie numbers.
