It all depends, but generally speaking not much.

The list is the list and one will get recalled in seniority order and BK does not change that.

If there is a merger one still gets recalled in the order of the merged list. And the merged list itself is determined by arbitration, which uses a different methodology for ALPA-ALPA mergers and non-ALPA mergers.

For example, in the case of the UAL/CAL ALPA-ALPA merger the pilots on furlough the day the merger was announced all ended up within a couple percentage points on the merged list compared to their pre-merger list. The senior pilots were still senior and the junior pilots were still junior.