The problem is (presumably) not the ATC controllers themselves, but the regulations which they have to work according to. There has been a lot of fuss about noise in the Gardermoen area from the time that the airport was built, and it's all about politics.
The noise abatement info on OSL states for example that "Pilots are urged to fly RNAV tracks on all SID's out of OSL, as this proves to give the best resultsin a very noise sensitive area".
Foreign pilots, who are used to flying over the densly populated areas surrounding most major airports in the world, must laugh their heads off when they arrive at OSL only to discover that the airport lies on the countryside, only surrounded by forests, farms, fields and a few small villages.
In my opinion the noise abatement procedures at OSL are a joke. The effect of the NAP-procedures is only that the arriving and departing aircraft at OSL burns off thousands of tonnes of fuel extra per year, just to please some local politicians.