As far as I know, the Town owns the line (and land) all the way south from Orangeville to wherever it connects in the main line in Mississauga. Only one land owner.
I'm not sure if it's been mentioned in this thread yet, but this Google Earth KMZ file, http://individual.utoronto.ca/sorailmap/, shows the location of most of the current and former railways in Toronto and Southern Ontario, including stations...
If it is actually part of a sanitary truck sewer system, its possible these are sewage pumping stations. I've seen them (drawings only though) at work, to allow sewage to be pumped up against a gradient in low lying areas. That's just a wild guess though. I'll follow up with the latest...
First response, without me mentioning the nearby golf course was that the valves must be old irrigation valves, especially with the hose on the wall.
Coworker said they're not used anymore since they would be split from all the freezing during the winters the valves have seen. Definitely not...
Yea I'll run them by him and some others at the office tomorrow.
I know that we offer infrastructure drawings to the public at little or no cost, perhaps Toronto can do the same if you contact them.