I work as a telecom engineer troubleshooting/programming the Ciena 5164 optical router used for Verizon and At&t. These companies and many of my colleagues know exactly what it was but the more interesting part that raised some eyebrows was the fact that cc payment processing and emergency services/SOS/911 calls WERE possible for most of the affected customers. This is key. (This all runs on the same fiber optic network and should have been ‘down’ also.)
I cannot overstate how anomalous the above fact pattern is because when our networks go down, they don’t go down in this piecemeal way.
Here’s the takeaway: The goal of a ‘cyber weapon’ is maximum disruption. Whoever deployed (tested) this ‘cyber tool’ went to great lengths to pause communication ONLY. This surgeon scalpel approach we saw was a MUCH more difficult task than to just ‘nuke’ the whole system so to speak. A tool like this would need to be tested a few times to ensure a reliable partitioning of the ‘Target’ [calls/data] and the ‘Not Target’ [911/cc processing].
I'm a patriot who loves their country so I will not say what 'it' was/is, but if you reread the above a few times, and ask yourself the right questions, logical deduction should provide the answer.
To your first question: No. The lines can be buried, but above ground equipment (fiber, optic routers/signal repeaters) must be used every 10 km in most cases unless it’s an undersea cable.
Telecom networks are laid out in a hub/spoke arrangement effectively. Traffic can be routed around brakes/inoperable equipment. One single fiber that blinks 1.25 Billion times per second (1.25 gbps) can also have up to 99 different spectrums (‘bands’) of light going over it simultaneously that do not interfere or react with one another. So basically one fiber can ‘do the work’ of 99 fibers effectively. It is for this reason that credit card processing/SOS/911/cell traffic/data/Internet/land lines etc etc can ALL be serviced by a single solitary fiber at a given site. In this context, the network is redundant because of its hub/spoke layout, but there is no hidden second network/lines just for 911/SOS/credit card payments.
What happened w/ the outages was like every single system failing in an airplane, except just the stuff necessary for you to land safely. This actually could be possible with an airplane because it has so many physical redundancies built into it. Telecom networks redundancy comes from its hub/spoke LAYOUT, not many different fibers running in parallel lines, etc.
Hope that helps.