I would actually doubt that, myself. The costs of building those structures were enormous, and by 1970 or so hydrogen bombs had become powerful enough and ICBMs accurate enough that it was pretty much impossible to build something that would survive a direct hit. Once that point is reached the only protection that the site has is its secrecy, and it costs the enemy less to hire spies and launch satellites than it does to build a new mountain. It's a losing race.
Facilities like these are a remnant of the civil-defense mentality of the 1950s. When the weapons were Hiroshima-style atomic bombs and the guidance systems were a guy 20,000 feet up looking down a bombsight, it was possible to build buildings that could survive an attack. Once you have hydrogen bombs and reasonably sophisticated inertial guidance systems, though, that possibility evaporates.
"impossible to build something that would survive a direct hit."
The Soviets had versions of the their enormous SS-18/R-36 missile with a single 25Mt warhead - these were presumably aimed at hardened sites like NORAD and Raven Rock:
Facilities like these are a remnant of the civil-defense mentality of the 1950s. When the weapons were Hiroshima-style atomic bombs and the guidance systems were a guy 20,000 feet up looking down a bombsight, it was possible to build buildings that could survive an attack. Once you have hydrogen bombs and reasonably sophisticated inertial guidance systems, though, that possibility evaporates.