The mysterious "freak building" on Monkland

So these two Conrad Poirier photos were taken in November 1939 at 5800 Monkland, in front of that Sutton building, next to the old Steinberg's, now-Gene Kooto building.
   The photos were taken in November 1939. But according to Lovells, the current stucture was built in 1953, so we have no idea what the short-lived freak building was.
   My initial suspection was that they were digging a tunnel for kids to stroll under to avoid getting run over on the street. They built tons of those around town and they're almost all gone now.