OPUS does use a network of CORS (Continuously Operating Reference Stations) and, simplified, works a bit like the post-processing you could do with your base and rover. It’s just done after the fact. You provide your rover data (which could be in actuality your base, sitting on the point for several hours) and they post-process it against the network.
NRCAN’s Precise Point Positioning (PPP) works differently. It doesn’t require a network of reference stations, it only works off of satellite orbit ephemeris (wher the satellites were precisely at each measurement) and atmospheric conditions (how the signal is affected), which can be refined after the fact. PPP works everywhere in the world, contrary to OPUS, but the results are similar. There is no baseline here, only your receiver is used in the calculation. You can still get centimetric results with an RS2 if everything was done right.
OPUS is a little bit less tolerant (unless there were upgrades recently) to file formatting and it only uses the GPS constellation with a pretty low refresh rate whereas PPP uses both GPS and GLONASS and will process higher refresh rates, so more data for the same observation time.
If you want info on any monuments and more specificly the one close to your farm, check this app from Ontario gov. In the COSINE retrieval section, you can draw rectangles around the stations you want to get the data from, select them in the list and then view the full reports with coordinates and other info.