It is probably a belt and braces action to ensure that (given they are separate networks) you do not accidently through in-action end up with two services, which indeed could run independently of each other. For users having a high dependency on access to the internet (WFH), this might be a very wise strategy for resilience - not just two connections, but connections from different suppliers over two entirely different infrastructures. Short of Paddy putting a JCB through the local shared duct, there ought to be a high level of resilience.
Where a change of ISPs is on the same network, the switching process is fairly clean - new service starts, old service ceases. Where they are on different networks, the existing service can be left active ... then folks complain that the transfer to Plusnet did not terminate the old service.
Your base assumptions are quite correct, the Plusnet provision will be over NTOR fibre and ONT network, nothing to do with the VM infrastructure.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
