@Curtain Rod - You put it much more eloquently than my clumsy attempt.
@Freehills - My understanding, albeit limited, is two fold: (1) The union contends that ARAPA IS part of your contract ergo there is contract violation; and (2) CX extending ARAPA for 25 years in exchange for the concessions the pilot group gave in 2008 should not have a 3 month statute of limitations to cancel.