A recent Quebec Court decision has stated that police officers cannot ask citizens to erase photos on their phones which capture the officers on duty. This adds to the notion that, fundamentally speaking, filming police officers on duty is completely legal. I wrote about this in a previous post.
The officers may, under certain conditions, request that you put away your cell phone, but they simply cannot take your cell phone, without warrant, to verify its content and delete certain images.
In fact, the Commissaire à la déontologie policière has recently released a statement confirming this policy.