I looked at signal 112 today and it does not have any plate on it, so a red-over-green-over-red indication on that signal means MEDIUM TO CLEAR.
I had a look at the detailed track diagram for the area, "CP MAKWA".
Signals are numbered by mileage, with an implied decimal point to the left of the last digit. So signal 112 is at mile 11.2 and signal 134 is at mile 13.4. In cases where there are more than one track, the track name is appended, like 111N and 111S.
The mileage is not precise because you could have two signals facing opposite directions on the same mast, but they have different numbers. For example, signals 133 and 134 could be on the same mast (they aren't).
When the Rail Traffic Controllers (RTCs) give out blocks to maintenance crews, they often use signals to indicate the limits of the authority they are giving. For example, "from signal 133 to signal 112".
While doing the research, I found an interesting article on Canadian signals. Check it out!
EDIT: Thanks Jeff Keddy for pointing out what signal 134 should have been showing.