The procedure is now in MATS2 and is covered by NATS "copyright" as it were. I CAN say that it is operated under strict conditions and during periods of VERY QUIET traffic rates. Probably ONE inbound on radar and certainly not when as Chevron posits
Do those units 'trialling' this procedure have a separate GMC position? I can't see an aerodrome controller vectoring inbounds whilst obtaining and passing IFR clearances plus operating stop bars etc.
In all honesty if you work at a unit with the traffic levels requiring GMC Tower and radar in the middle of the night.....this procedure is NOT going to be for you.
I can offer no further insights and thus (as a retired and no longer valid or current ATCO) I shall bow out.