Trial open cut mining planned: ~100Koz pa Au at a conservative 1oz/t Au, page-136

I reckon between the

1. Marcelo da Silva Pinto M.E. refinery;
2. the e-Reciclar facility in Belo Horizonte; and
3. CETEC university facilities in Belo Horizonte and Rio de Janeiro

there's probably enough independent parties working with the same ore.

I don't think they care about verification or JORC requirements too much. Cargo planes loaded up with gold (-Ag-Pt-Pd) dore bars flying out of Apui airport is the only verification that BBX and anyone else will need.

Given they have designed their own extraction process they would want to be playing their cards close to their chest instead of getting additional independent verification.