A bunch of specifics being pinned down would help. e.g. are the shelters inhabited, or just available? are they isolated in a way that stops them being raided? seasteading-based? self-sustaining? what stops people forcing their way in if disaster strikes?
It may be easier to fund off-earth colonies to this level, because it provides directly for individuals. Few would sell their house for a spot in a disaster shelter, some would for a ticket to mars.