Yes three units are classified as MOU (Well Intervention Vsl.): http://www.islandoffshore.com/fleet/fleet-overview/rlwi
Only the Island Navigator (under construction) is classed as Drilling Unit
There is also the Island Drilling ASA: http://www.islanddrilling.no/
That company own the Drilling unit Island Innovator: http://www.islanddrilling.no/our-rigs/island-innovator
Yes, these units work 2/4 schedule, at least when working in Norwegian waters, Don't know what schedule they may be on when working in British waters, GoM or Brasil etc., but you may know?
There may be other Norwegian vessels that is classified MOU, but ordinary OSVs, MPSVs and most CSVs work even time, whether in Norwegian waters or not. (4/4, 5/5 or 6/6, depending on which company and where in the world they are working)