You're receiving an 'image' of an 800 MHz frequency. GRE radios receive false signals in the 794-799 MHz area of frequencies generally around 864-869 MHz.
The easiest way to figure out what frequency is actually in use is to listen to the ~866 MHz band simultaneously with another scanner and figure out what frequency you're hearing that way.
It's probably one of the Ottawa area trunk systems. Do you hear the telltale EDACS beeps at the end of transmissions?
I don't believe I hear beeps after the transmission. If I do, does that mean it is possible to listen to a trunked system using a conventional scanner?
I get images in the same area on my Pro-106 from the City of London's EDACS system. Was quite puzzled when I found an EDACS control channel in the 790's one day haha