When I drove through Battle in East Sussex the other day I noticed all the cabs had silver locks on them that weren't there when they were being stood.

All I can say is that in the case of my cabinet it had a lock that was exactly the same green as the rest of the cabinet at around 9 am on the morning I was activated, and when I returned later that morning it had been replaced by a silver one & my line was now active. The other fttc cabs in the area still have the green lock and none are yet active