I seem to recall recently one of the Ontario airports (CYXU?) specifically telling pilots on the ATIS to contact Flight Service to close their flight plan. I have a vague recollection that back in the mid 80's when I was doing my private license at Buttonville that the ATIS advised pilots to use Flight Service to OPEN their flight plan...am I mis-remembering? If not, when did the "auto-open" process here come into place here?
On a side note, it seems the flight plan and the search and rescue notification are two separate things, on an IFR plan at least. When I did my IFR at an uncontrolled airport (Brampton) we would be talking to the Toronto Terminal controllers for the approach clearance back into Brampton. I think they have issues with potential conflicts with Pearson traffic either on their missed or us at Brampton and they always seemed to encourage us to cancel IFR. So, they would ask what our intentions were and we would tell them we want to fly the approach but will cancel IFR at KAPIK (the intermediate T-Turn to final fix) and that made them happy. When we crossed KAPIK and asked to "Cancel IFR" they would ask "Do you also want to cancel Search and Rescue as well?" and an "affirmative" was met with an acknowledgement that they would cancel IFR AND Search and Rescue.
Flying into an uncontrolled airport outside of Toronto, or into Brampton in actual IFR they will offer an 1-800 number to the Area Control Centre (not FSS) to cancel and then clear you out of controlled airspace and off frequency. If your IFR is open, they have the airspace blocked off for IFR traffic, so they want to know at the ACC when they can free that airspace up ASAP.
So, I guess it is possible to cancel the IFR "flight plan" when still far from a remote uncontrolled airport but leave SAR notification in place, cancelling that when on the ground.