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ATT’s botched network update caused yesterday’s major wireless outage
(arstechnica.com)
This is a most excellent place for technology news and articles.
It's not always about towers and signal.
There's call routes and service monitoring involved.
Call routing still has to happen to get you to 911. Service monitoring still happens to try directing your 911 call to another 911 dispatch center. If those two functions are broke, you get nothing no matter what.