I don't know..I'm not a combat engineer, but I don't think any bunker can last long if determined professionals are allowed to freely operate outside it. "nuclear bunker" means certain things about tolerance to over pressure, shock, contaminated air, etc., but doesn't do all that much against people with jackhammers and drills. The wikipedia page says the cyberbunker has 5 meter thick reinforced concrete walls, which would probably keep you and me out, but I'm sure can be defeated in time with civil engineering equipment. Beyond that, if you've got guys who know what they're doing poking around outside the bunker, there's whole worlds of things they can do.
These Danish cyberbunker people seem to share a mindset with the U.S. Ruby Ridge crowd, and they're both wrong. Making yourself an immobile target and defying state power in a developed nation really only has two outcomes: either you're not enough of a nuisance to provoke action, or you get crushed.