Actually, I saw a ton of them running between Lake Louise and Field BC last February when the snow was flying. The only way you could tell an AC4400 from an ES44AC was the cleaness of the unit (aside from the absence of the beaver logo).
They run quit frequently through Smiths Falls and they still are looking quite clean. After all, it was the exhaust that was getting them all dirty. By comparison, I saw an ES44AC coupled to an AC4400 running at full idle. The AC4400 was belching black smoke while the ES44AC hardly had any exhaust smoke.
Time to get out the toothbrush and scrub the weathering off the AC4400s so as to convert my HO scale models to ES44ACs.