A deal was struck as part of the post-strike agreement, about a common seniority list within Europe, containing both the 787 and 737 operation, irrespective of agency or daughter-company employed. So there will be no "skipping in the queue" - the longer you have been with the company (again, irrespective of equipment, base or employment agency), you can bid for positions according to you seniority. Some caveats apply, such as no-pushout-principle, seat lock, equipment lock and base lock may apply after a successful bid.
In my eyes this is the only fair system. It likewise offers 787 crew the chance to apply for the 737 operation if they so wish (equipment lock may apply initially). And again, there is no pushout, so this only applies when you and the other guy both want and both are qualified for the same position.