The MX3000 doesn't have any pantographs. The Holmenkollen-line had overhead wire but it had to be replaced with third rail 2009-2010 when the old carriages (T-1300) was going out of service.
Same thing for the Kolsås-line, There was overhead wire but in 2006 they decided to upgrade the entire line to metrostandard, and the line was fully opened in 2014.
So the MX3000 only runs on third rail.