Chevron,
It's so that if there is a change to ATS provider, the new one can't just copy the old procedures and they have to provide their own safety case to prove to the CAA that they are capable of taking over the task
I am sorry but I don't understand that at all.
Surely, NATS didn't pay for this work in the first place; it goes back to the days when it was nationalised.
Also, how can the ATS provider be changed?