Massachusetts 911 Call Outage

  "The Department has not received any reports of emergencies impacted during the interruption."

What does it mean, exactly? How do they know? They said they were able to collect numbers of people who called during outage and call them back, but could they manage to call *all* of them back?

“A preliminary investigation conducted by the State 911 Department and Comtech determined that the outage was the result of a firewall, a safety feature that provides protection against cyberattacks and hacking. The firewall prevented calls from getting to the 911 dispatch centers, also known as Public Safety Answer Points (PSAPs).”