They have been granted a lord F licence to prospect in the area for which he has mineral rights. Camborne Shaft is the only method of ingress into Wheal Busy.
If you notice, the shafts in Unity wood have been capped using batcastles; not for sake of the wildlife (as was demonstrated by Hallenbeagle) but rather for prospecting access in tune with Trounson's recommendations in his book.
It would be interesting to see a rework and how they try and adapt the conditions for modern techniques. Let alone what they do with the ore as the tin belt has long since disbanded. Or they could just open cast the lot, servicing their drills on the tears of conservationists and selling produce on the dark web.