All you crew that cannot understand the deal, no wonder you lost all your dough.
You transferred your shares to Opes in return for an off market instrument created by Opes. Note the words Off-Market. THIS WAS THE CONSIDERATION IN YOUR CONTRACT.
The value of this off-market instrument changed in comparison to the underlying share price, magnified by the level of gearing for your individual position. Opes was the market-maker. They created the instruments and calculated their value daily. They weren't backed by the underlying shares or traded on the ASX. You also owned the right to purchase the shares back from Opes at the expiry of the instrument, for the same price as you transferred them for. Therefore there is no CGT applicable to the agreements as there is no CG change on them.
In the mean-time, Opes borrowed money off ANZ and others, using the shares you gave them as security for the loans. This kept them afloat as large margin calls went un-asked for and unsettled.
Everything was great whilst the market rose, and everyone paid their dues. We all know what happened next.
The individual investors now see that their Opes-created instruments are virtually worthless and cannot understand where their shares are.
YOU GAVE THEM TO OPES IN RETURN FOR THE LEVERAGED INSTRUMENTS THEY CREATED FOR YOU.
Sad but true and no amount of hand-wringing or gnashing of teeth is going to change the facts.
ANZ are in an extremely sound position contractually as their dealings with Opes in lending money against the shares is entrirely normal and legal.
