Yes it's legal to tip others off to a ticket trap

Sandro Ianni is your friend

   Montreal cops have been picking on cyclists for the last couple of years, giving them tickets for no real good reason and being generally nitpicky, adding to the many reasons that you might not want to ride a bicycle in Montreal.
   At left is a recent ticket for a whopping $651 handed out Wednesday morning by officer A. Lelievre to cyclist Chris Lloyd, 40, of Henri Julien St., for allegedly obstructing justice because Lloyd warned others of some sorta bicycle ticket trap ahead.
   But it has been pointed that warning others of police presence is quite legal, as the 2009 case of Sandro Ianni proves.

Constable A. Lelievre seen issuing Chris Lloyd a ticket

   Ianni warned other motorists of a speed trap by flashing his car headlights. Others slowed down and a frustrated cop hoping to dole out tickets smacked him with a fine, which he contested and beat as this judgment shows.
   I no longer ride a bicycle as the seat hurts my butt but I spent about seven years as a hardcore urban cyclist: winter, summer, groceries, whatever. In those years I burned just about every red light I ever came across and never really got into much trouble for it, so I don't think I'd have much enjoyment these days on a bike.
  Thx to Marc Dufour for the tip.