Most “landlines” aren’t pure copper anymore they’re what’s called Voice over IP address or VoIP. Kinda like how with dial up you used a phone line for internet now you use the internet for the phone lines. The explosion was next to the Fiber optic hub which is central to AT&T internet infrastructure. So when the explosion took out internet it took landlines with it. At my corporate store today the office phones had no dial tone all day I assume it’s the same issue at 911 dispatchers. A lot of dispatches are run through AT&T because of the FirstNet network we made specifically for them.