Well I had two situations EX-HKG both first week of January, with high loads of student traffic. 2008, both me (AA Plt and CX SL) and my mom (CX SL) were upgraded, separate ticket. But in 2009, me (AA Plt and CX GO)travelling alone was upgraded but I noticed a family of 3, one of whom was CX GO was upgraded. So I dont know but I feel that lately CX been doing it by status, although the op-priority has switched between the time period of my two experiences.