Earlier quoted context omitted.
I think it's just too brittle. If we look for examples of similar bunkers, there are a couple military sites but nothing (AFAIK) that's been inhabited long term. Their concerns about keeping the guards on their side seems valid, that could turn out to be intractable. If the whole world does crumble, they'll have to be able to build everything from raw materials, including sourcing all of those raw materials. And so o…
We're talking about 2 small continents: entire AU & NZ, not bunkers. They can definitely be self-sustaining.
I agree that setting up their own little city out in AU or NZ might be a better idea than the bunker. Maybe they can even take over a large section of the land mass.
In my opinion, it'll still be tough to fabricate all of the things that modern society depends on today. Maybe they can do it if they really put their minds to it, but I would be surprised.