Around 1996 CX decided to back door the seniority list by having DECs. They did this by separating the freighter flying from pax flying. In 1999 union negotiations CX/AOA gave the freighter pilots a ONCE and ONCE ONLY chance to reintegrate into CX mainline, wef 1/1/00. Most took that chance. As part of that deal CX mainline pilots could refuse to fly the freighter due to CRM issues between CX mainline and ASL.
Since 2000, CX has had a lot of trouble manning the freighter so it decided to renege on a deal that was "binding in honour only" and give the remaining ASL employees a second "ONCE and ONCE ONLY" chance to come across to CX mainline wef 1/1/08. I think the offer was, in Godfather terms, 'an offer too good to refuse'. By doing this CX mainline pilots could no longer refuse to fly the freighter as there are no CRM issues when you all fly for one big happy company! It is win-win for CX. They don't pay bypass pay for the new CNs even though they are on the mainline seniority list and many are over 55. With a stroke of their omnipotent pen they have removed any lingering CRM issues and now the freighter can be manned by A scale CNs on the 400 - thus allowing CX to save face on the whole 'money saving' exercise of setting up ASL in the first place.
So we have two groups of ex ASL employees who have joining dates of 1/1/00 and 1/1/08.
Clear as mud?