I stand corrected on moving military kit around, but doesn't salt have medicinal value for treating injuries.
However from the video it seems that russia has ended the infrastructure running these mines, like they did with the nuclear power station, rendering what could be useful into something far less useful as no one is around to run it.
Cutting off power to nuclear power stations cooling is not a good idea, cutting power to salt mine ventilation is equally a bad idea you need people to actually run and maintain all this.