The reason they can do it there, is because the geography actually makes it possible - there are very very few places in the world where this sort of geography exists.
One of the guys from the local gliding club has experience in the area and is going back there within the next couple of months. Now the area has been 'discovered' by the gliding world there is intense competition to set and improve these records. Impressive though it is I would expect it to be eclipsed within 18 months!