I can only speak for Vancouver. New West, specifically, which is probably more crack-denny than other areas. But yeah, even Starbucks will hang fake "out of order" signs on the door because it's guaranteed to become an impromptu vein shooting gallery at some point during the day.
This happens in Europe, too. In Finland, in several towns it is not unusual for (the most nondiscriminating) public restrooms to be used for heroin injection, with the needle then disposed of in the toilet bowl, preventing the next visitor from using it and making the cleaner's job even more unpleasant. I am sure this has happened in Germany at least at some points in history when some cities were internationally infamous for heroin.
Cool story bro. Heroin use is practically nonexistent in Finland, opioid addicts use cheaper and easier to obtain alternatives.
I don't claim to know drugs well, but if it is being injected and causing a problem for public toilet operators, security, and cleaning staff, I just assume "heroin" because that is what people know. If you are more informed about substances, inform us here, too.