I think your last point "Expensive equipment and not suitable...

I think your last point "Expensive equipment and not suitable for every deposit and commodity" is a large reason why the JV didn't utilize XRT sorters at Barruecopardo. Oaktree had sunk a lot of money into this mine to get it running and they had probably hoped they wouldn't need more capital assets (expensive, more property at risk, a change in operations at site creating more risk, potentially unfit purchase for this mine), so they didn't go about purchasing them until EQR got involved, told them the mineralization looks similar enough and had a proof of concept that it would help. The other reason is probably that the JV required equal consideration or similar from both parties, perhaps they got to a sticking point where one party decided they didn't want to invest anything further.