Here's a photo of rotary 4 in Tacoma, WA while it was still in Milwaukee paint.The photo was taken sometime around 1973-1974.

Here’s some info I got from Jay Lentzner, the last active MILW employee on the west coast:

During the Convention, I had a good talk with the Chief Rules Examiner and he told me the story of why ARR thought the plow was a dud and promptly retired it.  Too bad they did not invite someone from Tacoma to come up and show them a thing or two. They tried it once in wet, heavy snow (just like in the Cascades!), could not make it work, and gave up on it!  One trip, and that was it. 
 
But not many railroads think they need a plow anymore.  Montana Rail Link even sold their only Jordan spreader.  (None of the young people in charge now knew how to run it, anyway.)