It isn't a worst-case though. They should have had the capability to resolve this issue with no network connectivity, which would be the worst case failure of the network control plane.
The article states:
> The defense in depth philosophy means we have robust backup plans for handling failure of such tools, but use of these backup plans (including engineers travelling to secure facilities designed to withstand the most catastrophic failures, and a reduction in priority of less critical network traffic classes to reduce congestion) added to the time spent debugging.
Another alternative is low bandwidth flag based roll-backs (for instances such as this where the network is congested but not completely lost).
My point being, it seems that modems are becoming less-and-less viable for out-of-band management.