I have noticed a wide variety of units on the CSX Albany-Buffalo Line. There is typically a mix of UP, CN, and CSX Units in a consist; however I have noticed several UP Only or CN Only consists.
There is even an occasional Conrail unit in original Blue/White color (and some with Conrail Quality) schemes.
I’ve actually been seeing CSX power on BNSF and CN trains, and that’s a long way for those little loco’s to go, beacuse I am nowhere near a CSX mainline.
(I’m as far west as you can get in North America on a Class One Mainline)
Some of the CN units you are seeing are probably coming down from Montreal via Massena and the St Lawrence Sub. I see a significant number of trains with CN power. At least one of the trains from Massena is actually destined for Selkirk, not Dewitt.