I finally saw one!
It was a GP15 leading approx. 4 hopper cars and a CN&W caboose I’ve never seen before. I twas heading southbound. What could have been its purpose?
And the location is???
I suspect that it’s a work train, and that the hoppers are probably ballast cars. Lots of action coming to UP North:
http://metrarail.com/content/dam/metra/documents/Bi_Level/OTBLAugust2010x.pdf
Wilmette, IL.