A couple of friends and I went out there today, actually, and had a look around. There's still lots of snow but you can tell where things are by anomalies in the snow. While we were traipsing around, one of the people who lives in one of the houses that can see the parking lot from their backyard came and talked to us for a little while. She said it was definitely old overflow parking for Doctor's Hospital (and was much more interested in the foxes that live back there).
The interesting thing to me, though, is that we peeked into the drains that are still in place in the curbs and could two different levels; the water was running in the second level down, and the separation between the levels was evident by a sort of shelf of concrete that looked like it had been broken. I've looked in a lot of storm drains in the past few years due to a predilection for saving trapped ducklings and never seen two different levels like that before. Plus, it looked like the "shelf" had exposed rebar, like it had broken off. My friends and I wondered if the lower level could be an old coal mine shaft, but it would be nearly impossible to tell without going down there when it's dry, and even then would be way too dangerous. We could tell that the water was running parallel to the street leading up to the parking lot. However, the storm drain on the entrance street didn't have the second, lower level.