swh
I think your confused, an ex Ka pilot or any airline pilot anywhere in the world will always have an ATPL/CPL once they have earned it. It isn't restricted to one airline (unless you were an MPL cadet) it can be used at any airline (might need to do a conversion if going to another country) where you are correct although the way you say it is wrong is regarding type ratings and being a qualified airline pilot for that company!
If a former KA 320 or 330 pilot were to be hired at CX or HKA/HKE then yes you are right they would have to redo some of the training programme at the airline they are joining (Indoc, ground school, sims) however CX could apply to the CAD to have a short course done for them a lot like how the DEFOs at cx do shorter courses than the cadets.