Revenue passengers get upgraded to accommodate for ID90 staff in Y. In DXB, this is automatically done by the system, which is why at exactly 60 minutes before departure, we know whether we are flying or not. I have tested this by constantly refreshing FABS at 61- and 60-.
Unfortunately this only happens at DXB, where the system chooses automatically exactly based on the priority rule in the staff travel manual.
In the outstations, the check-in agents and supervisors are supposed to follow the same rule of priority manually, but it doesn't happen all the time, unfortunately.