Freight traffic on Metra's UP North,Northwest, and Milwaukee Discrit north line - Trains Magazine

There is no freight traffic that I am aware of on the UP-N line.

On the UP-NW line, southeast of the connection in Des Plaines with the UP's UP/CP joint use line from Bensenville/Proviso, my experience is that there is only a couple of trains/day, consisting of a local run down to the Chicago Terminal yard (at North+Elston). 

Northwest of joint use line connection in Des Plaines, there is additional traffic that flows to/from the Chrysler plant in Belvedere and beyond.  I don't have clarity as to how much there is, but my experience is that it's not much more than perhaps 4-5 daily.

Lastly, although your text says MILW-W, your title says MILW-N, so I'll address the MILW-N: the vast majority of freight trains switch at Techny onto the joint use line and proceed to Bensenville, with only a few continuing straight into the city.