Historically, the arbitration over the collective agreement has always gone in favor of Singapore Airlines, or certainly for the last ten years that I know about.
By accepting to let negotiations be settled by arbitration (ie by the Singapore government), the pilots union (sorry, association, no nasty expat coruptive voting allowed here), accepts that a limit of 6 months backpay is the recommended maximum that has to be assigned by the company. If the pilots had accepted the initial settlement, then I believe the whole 2 years "backpay" would be applicable.
So, when the arbitration reaches its conclusion, everybody's happy.ALPA-S negotiators because they got a few more peanuts off the company, and SIA as they dont have to backpay massive amounts of dosh. Bingo! What a hollow victory. Expat pilots,do as we have all done before, get the hell outta there!!