There is a telecommunications link in the Western US that keeps several dozen or maybe hundred police, fire and rescue facilities connected and has some other government traffic. The actual owner of the fiber lost all the documentation on it and doesn’t want to pay for a full audit because that usually involves taking at least a few customers down and questions will be asked. If something were to cause large scale damage to that link, like a natural disaster where emergency services are in great demand, there is a good chance things wouldn’t go well. I’m sure it wouldn’t be a blackout but from the conversation that went on right in front of me it would likely cause some serious issues. I was in the room to help plan out a lateral expansion leg but only because I had gathered most of the info from the field so nobody really knew who I was.