The owner of Bolton Castle is of course Lord Bolton, as did much of Wensleydale in past times. When the WRA was set up he did, I understand, suggest building a halt beside the Castle at his own expense as if the railway terminated there it would undoubtedly make the visitor numbers to the Castle increase dramatically. People could alight, visit the Castle, have tea and be back at the halt for the next train.
Lord Bolton leased the trackbed from Redmire to the Railway at a peppercorn rent, also including most of the further trackbed to Aysgarth. This is still the case, although there are a small number of short sections in private hands.
How about a deal with the new owner? If he wants to relay Redmire-Aysgarth he would need to traverse WR property. In return WR gets running rights through Aysgarth.