There is really no chance on Norway backing out of the Nato system, since nato funding is the only way the current modernization program of the EW system could happen.
Both the Swedes and Finns have sought deeper cooperation with Norway and NATO the last few years, particularly in procurement matters and training.
Since Norway has a rather small military structure, it has proven better to corporate with a nation of similar size with similar needs when dealing with suppliers. (More true for the army side om things so far, much of the same equipment even before cooperation started)
Regarding training, I think at least the Swedes has taken part in every major exercise of any branch in Norway the last 5 years, as they try to integrate their operations with NATO.
On another note, it's quite entertaining to follow the debate in Sweden about Nato menbership. They still think they are completely separated from nato. That's why the Swedish commitment in SFOR and KFOR was reported as "UN Operations" by politicians , as is their force in ISAF today.
