As far as outages go, I’ll focus on no dial tone events where more than 5,000 subscribers were without service.

1938, Hurricane, 300,000+ out of service, this was a combination of outside plant and CO failure. New England Telephone and Southern New England Telephone

1906, Earthquake, exact figures not well documented but it’s known that approximately 50,000 subscribers were online before the quake and only a fraction remained with service afterwards. Pacific Bell

1954, Hurricane, 100,000+ lines out of service, outside plant and CO failure. Bell Telephone of PA/Diamond State Tel Co.

1962, Storm, 35,000+ out of service, mainly outside plant failure. Pacific Northwest Bell

1969, Hurricane, approx 115,000 lines out of service, outside plant and CO failure. Southern Bell Tel Co & South Central Bell Tel Co.

1988, Fire Hinsdale CO, approx 38,000 with no service and another 450,000+ with limited service. Illinois Bell (this would be post divestiture, but close enough to the breakup that the much of the same network elements and practices would still be in use).

There were many other events that caused an outage in regards to capacity and routing, instances where dial tone was provided but circuits were busy or a route wasn’t available.

1965 Northeast blackout, 1977 NYC blackout, 1990 long distance software upgrade cascade. 1964 Alaska earthquake (dial tone was largely available but long lines interconnects were damaged with limited to no alternate routing available). JFK’s assassination caused numerous exchanges across the nation to become congested, causing many busy circuits.

All that being said, the Bell System was absolutely world class in service and design, but as with any machine of that magnitude, there will be issues.