If I were a manager at the mining company that purchased the drones, I would be worried about retaliation in kind by workers who obtained a similar drone.
That would mean your workers had too much disposable income and free time. You should reduce both as a precaution.
Why drones - invest in smart ground based flak cannon manufacturing.
If we can't fly -- we won't let anyone else either - old anti aircraft moto.
Indeed. Here's something somewhat related, from PyCon 2012. It deals with using computer vision to fire a squirt gun at squirrels. The principle is basically the same.
Managers at South African mining companies already have good reason to be worried about retaliation from workers. Details in my other comment on this thread - but in short, buying a drone is really just throwing fuel on an already well-fueled fire in this case.