Earlier quoted context omitted.
Calling it a bunker might be overstating it. Maybe some are like bunkers or some have been reinforced. It’s hard to say. Sometimes these central offices are put in really old buildings. Sometimes they are even put in regular homes in a neighborhood. It’s simply based on where they need the connections/circuits and have access to electricity, etc.
No, a lot of AT&T buildings were built as bunkers, well blockhouses, during the Cold War. The typical "reinforced" criteria was being able to handle 2-3psi over pressure and storm force winds (70mph). This particular building is an old AT&T-cum-BellSouth-cum-AT&T tandem office. It's where end offices (that connected to actual customer phones) would be connected together and connected to inter exchange carriers. AFAIK…
In both cases it was a housing tract that was allergic to ugly buildings or something. The vast majority of RSUs looked like smaller versions of the CO. Gray cinder blocks and asphalt.