See P7, people do want to talk about this!! Nah-nah!!
We have also been told that BA ets performing the STAR shall not delay other inbounds like MacDoris explained.. We have had instances of some a/c starting the procedure then being vectored in the later stages so not to slow others down.
It does seem to work if you have a a bunch coming in, and the last one is BA.
Kfw makes and intresting point. While the trial requires quite a few jets to do the procedure, there is the issue of "I can offer you straight in at high speed" or "You can do the procedure at standard speeds and increased track distance".