I was only told, in some detail by Sid Harvey about his work-friend (they were near neighbours too) who was shipped out to Canada. They were told that he was going up to Birmingham(?-not sure about this to be honest) to assist setting up the new sniper production line. It was a secret to start with until some months later when it was a bit of gossip spread through the H&H works. No date and unfortunately Sid has gone to join the rest of the No4T conversion team. BUT, if I was a betting man, I would venture to suggest that it would have been for the 71L/90L batches/era/time. I say this simply because Harvey said that while H&H did keep a sizeable reserve of suitable rifles in the vaults (the old cellars, which still had the long rifle racks fitted, with a small hole bored on the top wood shelf section where the bolts could be inserted while/if the rifles were being converted), they found it far, far easierand simpler in time and machine setting etc etc if the rifles came in from ONE source. Much like buying a fleet of Fords made in Cologne as opposed to a few from Dagenham, some from Seville and others from wherever. The fact that they were all the same made production line conversion simpler. They could also deal directly with BSA managers for day-to-day matters.
That's the reason LB took a big pile of, probably, same-day production and using the production like technique imported from H&H converted them knowing that when a certain machine was set up by the skilled machine setters* it was good for all of them
Regarding the Mk1 scopes. I think that it's a case of repeating the old saying we used to have. You go to war with what you got. You can have what you need, later. But you can never have what you want!
* The machine setters at Enfield and elsewhere were not 'skilled' workers such as the apprentices etc etc but were the very top of the pile from the UN-skilled workers and were highly regarded by the workforce and managers.