They won't get the option to decide whether or not they will be providing redress, but they will no doubt fight every step of the way on who should receive any from them.
If one takes 1750 survivors (roughly the number given by the WT's own records) who could potentially seek redress, multiply that by the average $Aus 64,000 (one of the commission's suggested figures for weighting redress), you get $Aus 112m (52m pound sterling / $US 80m). That would likely be spread over 5 years or so.
I think the survivors who've found the strength to take their cases to court in the past probably have it right - the WBTS won't take child safeguarding seriously until they make the financial calculation and realise things can no longer go on as they have been. Still not sure I can wrap my head around just how pig ignorant the GB are.