As far as I am aware, Manchester are conducting the same trial.
I'm not sure about Heathrow, but I can understand the confusion with conditional clearances at LHR as they are issued to more than one aircraft at a time.
Predominantly at BHX its normally one aircraft that gets the clearance such as "after the landing A320 etc, line-up and wait"
Runway incursion is evidently the hot cookie at the moment, but is this:
1) a step too far:
2) too restrictive;
3) insulting to pilots
4) justified in the name of safety
5) a good idea but needs modifying slightly (ie only given to 1 acft and not multiple ala LHR)
what will the trial conclude?
BBB