If you start popularising all local unconventional names, there is no end. Cannot comment about Hyderabad. But Kovai, Nellai, Trichy, Thanjai, Kanchi are the popular / short names for their full names Coimbatore, Tirunelveli, Tiruchirappalli, Thanjavur, Kanchipuram.
Railways should refer the names by their official names only - not the way how people in neighbouring state call. Just because Mangalore comes under Kerala's Palakkad division, can they change the name of a Karnataka city? ЁЯдФ