I've made a quick update, not heavily tested though and I'd appreciate you trying it out for me. Download the test zip file ATSCCanadaBeta.zip from https://skydrive.live.com/redir.aspx...F37BD7B107!236
There's a new option #9 "Custom (Force a Canadian guide update on a US system)" which should address your scenario.
At some point I might add quick links to major cable and satellite systems but that could become a large task. For now, you'll need to do some custom edits.
Here's what you'll need to do...
1. Get the guide ID
Navigate to Tasks, Settings, TV, TV Signal, Set Up TV Signal. Set up Media Center to use the guide that is most appropriate for your needs (for example, I selected the Rogers Mississauga lineup which has all of the OTA digital channels listed). Next, navigate to Tasks, Settings, TV, Guide, About Guide Listings and take note of the 8-9 digit ID number.
2. Set up Media Center TV using the US as your geography, selecting the correct type of signal (example, Digital Antenna + Cable STB).
3. Edit the files
Open XMLTask/ImportCANCustom in notepad and replace 189833220 with the guide ID you collected above.
Open MXF/CustomGuide.mxf in notepad and replace 189833220 with the guide ID you collected above (note that this appears in 3 places in this file).
4. Run the hack
Right-click on USGuide.bat and select "Run as administrator"
Hit the number 9 on your keyboard
That should do it, but like I said it hasn't yet been tested so please share your results.