No it's not entrapment as the others are saying. However, if he is tagging people for going above 50 in what clearly is not a 50 zone then you should be contacting CPS directly complaining that the officers is illegally pulling over vehicles for speeding that are speeding and you have proof.
I'm quite positive this is the type of activity CPS will not put up with simply because it can easily lead to bad publicity. I would seriously complain to CPS, contact the calgary herald with your photos and story and furthermore complain to your alderman how are police are using tactics like this which clearly are not justified.
It's one thing if they were writing tickets in that appropriate area but he clearly is not.
Secondly I noticed a post where a person said the maximum sign is a maximum speed. It's actually not. You can't go around driving 50km/h in a 70km/h thinking you can. It's just as bad if not WORSE than driving 90km/h in a 70km/h zone since it is inheritely more dangerous than speeding and is proven to actually lead to more accidents since the people that want to go the limit will usually going to a variety of lengths to attempt to pass you even if it's not necessarily safe. I had this happen to me just last night and I watched this guy in a truck pass this old lady who was driving 35 in a 50. He actually drove up on the side walk and went right past her. Also if you go 50km/h in a 70km/h zone with a cop behind you i'll be you money the cop will pull you over. Yet if your going 80km/h in that 70km/h zone they wont.
Fight the ticket to the end of the world though. Realize though this cop is being paid handsomely though to be in court with you. If i recall from my days with CPS they get paid double pay for 8 hours for being requested in to court. I would highly urge you though to put this into the herald so that others drivers that got caught doing this can realize they likely weren't in the wrong.