Ryan, thanks for trying, but... I have training as a signal maintainer, and follow practices and techniques closely. My comment that the signal housings were SafeTrans plastic castings (versus, say, US&S or older SafeTrans aluminum boxes) should have been a clue I knew my way around signals. This question was not generic, I was asking about specific practice on these ex-Soo 4-color heads. Four-color heads are typically for special, specific conditions on other railroads. This ex-Soo line had them everywhere, as (apparent) normal absolutes and intermediates, a practice new to me.
First thing I noticed is the color positions are not usual North American practice - the red is at the top. Since I didn't have the ability to get off the train and examine the lenses for color placements, I can only guess whether it's red-lunar-yellow-green, or maybe red-yellow-green-lunar, or even possibly red-red-yellow-green or red-yellow-yellow-green under a system where diverging and advance diverging aspects can be shown in a single head. These "alternative" aspect practices are sometimes seen in transit systems.
I'm pretty sure these signals were installed by Soo and are not new retrofits by CP. The way to tell is the older design of a visor for each lens, rather than snow ("Vader") hoods. I'm sort of hoping that one of us who is out of the Chicago or Milwaukee area might be able to tell me what's going on.
