Thank you for explaining what happened. As I figured it was people (mainly studends by the sounds of it) who have moved due to school or whatever. Of course they would get a pin number forwarded to them by mail because their mail is probably getting sent by their parents or they have it diverted at the post office. People who have moved in or out of an area create small issues for a municipal election, because of the limitations and requirements of voting for just a small geographic area. Now just remember the big picture.. a 30% increase in voter turn out. Just imagine if the rest of the eligible voters could have been able to vote!
The other point of focus here is that for a federal election, you would be able to vote no matter where you moved to as long as your a Canadian citizen, so people who move for various reasons would still most likely be able to vote as long as they have their mail forwarded properly.