i should imagine the noise is just extreme cold and wet, something our disc brakes dont really ever have to endure…so the noise will clear generally once warmed up or after braking for a while….
as for the brakes working in cold, my xts were superb last night, even down a rocky snowfilled descent they stopped me dead when i feared i was going to fast and expected to just skid the front wheel braking and fall off, stopped me like in dry to be honest if not better…..
mine did warble a bit from time to time thgouh, like it was juddering, but again that must be the temps, as once brakes were used again they were totally silent and warble free….