Since both are ALPA, it depends on the results of the negotiated SLI. Or whatever the mediator decides if the two unions can’t agree - which is probably the norm. Based on the Alaska-Virgin example, it will likely be a mix of relative seniority and date of hire.
AS-VX formula:
60% longevity, 40% status/category
Harmony model meaning the formula was applied straight through 60/40 with no other ratios/re-doing
No fences
Certain restrictions to protect current CAs on both sides in case of future base closure/reduction