I believe the precedent was set when 'London City Airways'(LCA)was integrated into the then 'British Midland Airways'(BMA).
When the 'Gulf War' broke out,the LCA guys were kept on,whilst those above them on the seniority list were laid-off.
However,it would seem that the individuals concerned in the current dispute, left 'Commuter'or 'Regional'of their own free will,and therefore should be treated the same as any other pilot joining from another company.On the other hand ,maybe they just transferred from one'department'to another.....I'm confused