Depots are located at Kowloon Bay ( for Kwun Tong Line ) , Tsuen Wan ( for Tsuen Wan Line ) , Heng Fa Chuen ( for Island Line ) , and Dream City ( for Tseung Kwan O Line ) . Since the opening in 1982 , the Tsuen Wan Line is the only line whose alignment has virtually remained the same for the past 23 years . For example , the Kwun Tong Line 's alignment has changed twice since its opening â '' the taking over of Tsuen Wan Line from Mong Kok to Central , and the taking over of Eastern Harbour Crossing section by the Tseung Kwan O Line .