While it doesn't happen to me all the time, from time to time I do run into someone I know outside the work setting. In one case, it is the mother of one of my daughter's friends. They live about a block away and 2-3 times a month we end up on the same bus in the morning. It doesn't happen nearly as often in the spring/summer/fall, as I am usually riding my bike. Of course, if I am over at Withrow Park or at some school event, then it is hardly surprising if I run into people I know from the neighbourhood, and that doesn't really count.
Last Thurs. I ran into one of the city planners I know on the subway, and we had a bit of a chat. Then Sat., I was over at Danforth Tech and saw a former co-worker. He seemed pretty happy (and glad to be in a new job). And periodically I run into other people I know. I'm sure it would happen more if I didn't move around as often (and simply knew more people from school, for example). And I am quite sure this happens far, far more often in Charlottetown or St. John or St. John's, but it is still always amusing to me when it happens.