 In the late 1980s , it was decided to upgrade the Røa and Sognsvann Lines to metro standard . This would allow them to use T1000 stock . Twelve T2000 were ordered in 1991 , and would be sufficient to operate the services on the Holmenkollen and Kolsås Lines , that would retain an overhead wire . The development costs for the T2000 were in part subsidized by the government , as the high @-@ tech product from Strømmens Verksted ( by then part of the ABB Group ) and AEG was seen as a future export product . The trains were delivered in 1994 and taken into use in 1995 . The same year , the metro started operating all services through the city center , connecting the western and eastern networks . 
