Large organizations have a tendency to demand custom solutions, and then they want to throw the switch all at once. That is pretty much opposite the bottom up, self-organization, of HN themes.

If you could "bubble up" a "good enough" 911 system, it probably would be reliable and probably would scale. But the contract will be given to the company which will say they can provide a big custom solution on a deadline. It's almost worse if they believe it themselves. A dishonest vendor would at least understand the scale of the problem(s).