I was recently in Rostock Germany and I saw plenty of pedestrian areas closed to traffic but with signs saying "feuerwehrzufahrt" which means "fire truck access road". The pedestrian area was protected with bollards or fences that could be unlocked by emergency vehicles who needed access.
So many problems that we Americans fight about have been solved ages ago in other countries around the world with far less drama. We're not as unique as we think we are.
Yeah, presumably the same way they solve it everywhere, which is that police, ambulance, fire, and city all have the same keys to the same bollards. And when they don't, they just use their bolt cutters or drive up over the sidewalk. No biggie.
I could see something like this working out well if appropriate provisions were made for these things.
State St. in Madison WI is paved, but only allows mass transit, emergency, and local deliveries.