In all of my decades I recall only one telephone outage one time, at home. A truck (or something) had snagged a line feeding the house. It was repaired less than an hour after reporting it.
And I'm nostalgic for that kind of reliability, but it's gone now.
I was chatting with a tech who was installing a new county 911 system a few weeks ago. There was a time, not so long ago, when 911 had been robust: Fixed circuits to multiple different areas (to walk around network issues). Slow, redundant, robust analog modems on leased lines for caller data and call control. Eventually, things like PRI or T1.
Either way, there were great racks of redundant gear at the 911 PSAP for managing calls.
But now? It's just VOIP over the public Internet. 911 calls get the same not-special class of service that posting this comment does. The huge gear-filled racks are gone. In their place is a router and a switch, and a collection of dispatch PCs.
(There's a backup IP connection, of course. This backup connection uses cellular data.)