Other way around I think Brucey.
NCL has been "advertising" flights as Viking (on screens etc), and passengers have been booked with Viking by the agents. But my understanding is that the aircraft, crew and flight number changes from VIKxxx, to SGXxxx, or OHYxxx when people turn up at the airport.
All VIK flights from NCL have so far been Saga Airlines, or some other Turkish outfit called TrailWinds. Though there is definately a VIK flight number on a flight to Verona tomorrow! (well according to the website). Wonder if that will change too?
RTG!