I had one game where Moscow fell but allies won…because Germany fell to US 2 moves later. Then US added a few men in Western US on every turn to prevent Japan takeover while focusing most US/UK effort on Europe and eventually rescued Moscow.
So it is possible but unlikely, I believe only if Allies are within 1 or 2 moves of taking Berlin. If allies can’t take and hold berlin then it’s impossible because then Germany can go 1-on-1 with UK and Japan can go 1-on-1 with US. At that point it could take ages to resolve the game.