GRZ did do a feasibility on a combined project and it would work, but for some reason everyone assumes that means one large pit, which is not necessarily the only concept that would work.
KRY's current plan involves several pits some distance apart. A combined mine could have seperate pits but a common processing mill using conveyors or truck (depending on the distance) to bring the ore to the single mill.
GRZ's proposed mine would be one pit with a conveyor to bring ore from the pit to the processing plant. The plant is some distance from the pit because all the closer ground is not suitable for building the plant on.
This is purely academic at this stage. Rusoro and the CVG would have a hard time finding a billion dollars to re-engineer and build just Brisas let alone doing a combined LC LB project within a reasonable time.