I think they would require a bulk UG mining technique to...

I think they would require a bulk UG mining technique to feasibly get the mining cost low enough to mine this orebody so I doubt they will be able to mine open pit and UG concurrently, as sub-level caving involves surface subsidence which is incompatible with open pit mining. Maybe there are other adoptable UG mining techniques that don't cause surface subsidance but I'd say most of these techiques are too low tonnage, so would only add very expensive incremental tonnes to the open pit ore feed IMO. My guess is that the UG option will involve significant pre-production CapEx in the form of lots and lots of UG mine development and supply of UG mining equipment and automation systems. Esh