I don't think they do split the numbers evenly between the FTOs. That's an illogical approach and would almost certainly mean selecting some inferior candidates based entirely on the FTOs they came from. It should be entirely about how the candidates perform, and have nothing to do with anything else. That's why I think BA select the best from the applications all three FTOs send them. Picking the best applications is the only way to ensure you get the best candidates.