From what I saw in the email about the arbitrated large RJ rates at ExpressJet, they are using a seniority based system instead of an override system. The seniority based system pays a percentage of senior pilots coinciding with the percentage of large RJs the higher rate, regardless of the equipment flown. A junior pilot could fly the large RJ only and would still be only paid the small RJ rate. This makes sense to me seeing how (ASA) has always thrown the junior guys under the bus.