It's not just when the mining company themselves are chartering the aircraft.
An acquaintance told me the story of how a group of locals in his far-from-a-big-airport area, all contractors at the same mine, were sick of the long time it took to get there and decided to charter some piston twin to transport themselves.
When asking permission from the AD operator, the answer was a resounding NO. Twin pilot and twin turbine or you are not welcome with workers here.
(Private pilots in SE aircraft on business not related to the mine are allowed to fly in.)