Agents provocateurs du Québec

Predictably enough, protestors were out in force at the Canada-US-Mexico summit at Montebello, Québec, voicing their opinions and those of many other Canadians. Which is all as it should be.
However, what is not as it should be is the allegation, and it looks a very convincing-looking allegation at that, that some of the demonstrators may have been planted by the Québec police in an attempt to provoke violence and generally give the protest a bad rap.
The Sûreté de Québec has a reputation for heavy-handedness and underhand operations over the years, which makes the allegation all the more convincing, although it is difficult to understand what their hidden agenda might be (unless it was dictated to them from above...)
The evidence in favour of the allegation includes:

• the three men appeared not to be known by any of the other demonstrators;
• one was clearly carrying a rock in an area of specifically peaceful demonstrators;
• all three were wearing exactly the same type and brand of boots as the regulation-issue police boots;
• all were masked, albeit unconvincingly, and fought strongly when attempts to remove the masks were made;
• at one point, one of their number was seen to be calmly discussing something with police officers (as opposed to arguing or screaming abuse);
• none of them ranted and raved or even argued when "arrested" - they were suspiciously silent;
• when "arrested", they calmly disappeared through the police ranks and were not seen again;
• no names of the arrested men have been reported, and police are refusing to comment on the matter.

Update:
Later, under media pressure, the police admitted to planting the agents, so everything is OK again.
Errr, now hold on...