Yes, it's true. The turrets fitted to the Lancaster were Nash & Thompson hydraulically actuated power turrets. The N&T turrets were keyed into the aircraft's hydraulic system, which also actuated undercarriage retraction and flaps. System pressure was provided by engine driven pumps (EDP) and each turret was keyed into a particular EDP as follows: Tail turret, port outer, front turret, starboard inner, mid upper, stbd outer and under turret if fitted, port inner.