Both work, odds are I was the very first non RPA/DB person to use the leap card on a nitelink. Driver was a little puzzled, so the crash course in issuing a ticket was given in 10 seconds
Just one minor point on the bus, the 'City Centre Fare' is available on leap, on the drivers machine, its in a second menu (square button below the main buttons, 3/4th down 'Shopper Fare')