Well we have most the town stuff covered at Bigfoot in Mission out in BC. The point about buildings being used to hunker down in by large groups is a valid one.
The other thing to consider about buildings is FPS limits and fire control.
As well as safe access, we have had two incidents, one guy hit his head on a half height door, lots of blood no serious damage. I bounced off a door that had been barricaded, apparently very funny to watch, but my shoulder disagreed somewhat. Both were easy fixes, bright orange around all half doors and no barricades.
We considered tunnels, but decided the animal, water, and problems with smoke when allowed made it not worth while. Short covered sections of trench may show up next year.
Space & cost are the biggest issues, we have a small field but lots of dense vegetation as well as several covered approaches to the town area.
Here is a slightly out of date interactive map, there have been some changes over the summer. Click on the numbers for images of that area.
Interactive Map (Not 56k friendly)