The ex-BMI guys were offered promotion from RHS to LHS in accordance with their relative seniority in BMI so an FO who was close to command in BMI would get his command in approximately the same time as if he had stayed in BMI.
As BMI was operating the A330 they were also granted alleviation for out of mainline seniority transfers to LH in accordance with their pilot percentage against main line. I think about 5%-7% allowed early transfer as they would have realistically expected to go to the 330 within BMI.
It's a little hard to grumble about what was, after all, agreed upon the acquisition.