I can confirm that you can use AirPrint with AirPrint-enabled Canon printers, and yes, from other iPhone / iPad apps in addition to Canon's own Easy-PhotoPrint app.
My printer was completely set up and working on a wireless network (when printing from a Mac) except for the "No AirPrint printers found" message on the iPhone when attempting to print from an app.
The fix was to:
- Download the "Printer Update Utility" software from Canon (which updates the firmware)
- Turn the printer off and on (but don't worry, an instruction checklist is shown when you start the utility).
- Connect the printer via USB to a Mac (updating the firmware won't work via the wifi connection)
- Use Canon's "Printer Update" software to upgrade to firmware version 2.0
- Turn the printer off and on again.
Done. I didn't have to re-enter the wireless network information; printing from an iPhone worked automagically from that point onwards.
Hope this helps!