BMI captains and FOs will be at the bottom of their respective fleet lists. They can submit a bid (IB1) like everyone else. They may get a trip line (a line of work spread out over the month) or they may get a blind line (more likely) until they gain more seniority within the company.
A blind is a line of work constructed by ops once the two bidding processes are complete. Blind line holders can submit a preference prior to line construction, e.g. late day-trips or 4 day tours preferred or anything you like. Ops will try to accommodate preferences so long as the work is covered. About 3 weeks prior to the start of the month your roster is published. This is exactly what BMI crews get now so no loss of TUPE,
Its actually better than the current BMI situation in that you can swap trips with the overtime list or other crew. You can add trips as overtime. You can discard trips (with loss of credit / cash) using a system called eMaestro. Again BMI crews are not any worse off than their current situation and NO BA pilot is disadvantaged by a BMI pilot bidding ahead of them......WINNER, WINNER, CHICKEN DINNER.