Just some anectodal evidence from my recent trip:
25/1/17 BA2157 LGW->ANU
First day at the south terminal and special assistance followed by Club World rigorously enforced (sorry didn't catch the remainder was in CW)
Fast Track enforced
1/2/17 BA2256 ANU->LGW
Special assistance followed by Golds only followed by Club World rigorously enforced - which was a welcome change after the total bun-fights I remember from the old terminal!
No such thing as fast track in the Caribbean! However CW check in (required for vouchers for the brilliant new lounge) opened first.
Hope this helps