Ann: Mt Lyell Copper Mine Prefeasibility Study, page-7

It's a good option to have for the next ten months but they then have to make that decision on whether to exercise it and pay the exercise fee of US$10mil and replace enviro bonds(A$6mil).
IRR(pre-tax) of 22% on Nov copper/gold prices is low that rises to 27% on current prices. Payback period of 8yrs from decision to mine or probably 6yrs from start of production is a lengthy period. Total capital drawdown of A$360mil currently looks a large task to arrange with probable debt finance of 60%(A$216mil) and equity contribution of 40%(A$144mil) but definitely not impossible.
I think at the end of the day that the seller, Vedanta might be on a better deal than NCZ with their royalty deal of US$300mil plus option exercise and commercial production payments totalling US$20mil.