A telco I used to work for did this like two decades ago but even better, they mapped incoming support calls (customers) to stations, and if more than N came in during a certain period for the same DSLAM it triggered some kind of alert.

Same thing happens (should happen) when you visit your ISPs website and look for registered downtime — many requests from one zip code from multiple ips should trigger an alarm if the isp is competent.

In my last job our main “is everything okay?” monitoring dashboard had RPS, latency, 500 rate etc and a line for the number of user issues reported per N requests served. We didn’t alert on this but it was a useful way to detect issues that were subtle enough not to trip up our main alerts.

My company does. :)