T4&T5 Long haul in my experience always seperate line for F/CW/Gold/Silver.
On S/H 767 from T5B I've used fast track boarding too.

T5B seems to be prepared for it, while T5A does not.

On large BA outstations like JFK there are dedicated lines for Premium PAX. Although sometimes the Y line is actually quicker.

OP says Pre-Boarding however. Do you mean seperate boarding for premium PAX before everyone else, or general fast track boarding?