Thank you for the comment.

Mininet did help me a lot during the initial phases. The main reason I made the switch to containernet(mininet-fork with containers ) and then to containerlab was because I wanted to run an actual NOS image as part of my topology. That was really what pushed me to try and switch to other options.

Yup, its a different experience. Sometimes, you end up learning something you never even intended to.

As for the circuit planning, I'd guess that they have circuits map on something like Netbox and using a intermediary system that maps a customer's location to the nearest circuit. Though, I don't know how they handle the optimization side of it to prevent cases like what happened to your neighbour.