Phase 3 of the airport construction is now under way. It was supposed to start about a week ago, but this being Bahrain, it didn't and started today. Under the old phase2 construction, just over 1000m of runway 30 threshhold was displaced. Now under Phase 3 it's a bit over 1400m, leaving about 2200m for landing (7 thousand feet for those who work in imperial). The hours of construction are 0300-1130z each day. During those hours the threshhold is displaced, outside those hours as far i know it's not.
Using the standby runway would be a nightmare of delays. It's the main taxiway running by the apron, if it's used as the runway you basically wouldn't be able to push off the gate if there was an aircraft within 50 miles on approach. They are eventually supposed to operate off that runway under phase4 or 5 construction, and i'm fully prepared to sit at the gate for 2+ hours whne that haapnes.