Interesting!
Records indicate that much (if not all) of the .56-.50 ammunition acquired by Canada in 1866/67 for use in the several thousands of Spencer rifles and carbines hastily acquired to help meet the Fenian Raids threat (and also for issue with the 3,000 .50 rimfire Peabody rifles and 1,000 .50 rimfire Starr carbines acquired at the same time, both of which would chamber and fire the Spencer cartridge) came from Sage Ammunition Works.
I have always thought that, with the mixed bag of breechloaders they were getting, it made uncommon good sense, logistically, to limit the cartridge supply to the one cartridge which could be chambered and fired in all three types.