Base of train matters at the time of deciding the zone of the train, take some example...Magadha Express runs b/w Islampur and NDLS but now have RSA with Shramshakti a NCR train and have it's base(Primary maintenance) in CNB so now it's an NCR train. BJU-LJN Express has RSA with Chitrakoot Express but the base of the train where PM is done is BJU so it's an ECR train.