My understanding is that BMI crew will be joining Eurofleet with an opportunity to apply for Mixed Fleet if they would prefer that lifestyle mix of long and short haul; it will be subject to success at interview I believe.
While on Eurofleet their salary from BMI would be maintained but they would be unable to transfer to WW; on Mixed Fleet they would be signing a new contract, accepting the salary and terms and conditions of that fleet and could benefit from promotion opportunities. Either way, longhaul legacy fleet is not currently an option (but who knows what would happen in the future).