Major fighting in the north basically stopped by November 1944. If the Soviets had really pushed, then maybe they would be able to take Narvik in an overland campaign backed by flanking amphibious assaults as OTL. No way do they launch an amphibious attack by submarines (!!!) as far as Trondheim.
Now, if relations between east and west sour immediately for whatever reason, then perhaps a People's Republic of Norway with its capital in Narvik could emerge, but that's about it.