How it works is very close to what you described except for the last part. So let's take MMA, for example. If a railway decides to acquire additional lines, so expand the network, or abandon some of the lines, which was the case with MMA, they have to apply to the agency for the amendment of their certificate of fitness. That's all they ask. The agency will investigate what kind of impact the change in their network will have on the insurance, and so whether it is still adequate or not.
