I know a big mid-rise apartment complex sits on the site of our old house.
I think I can shed a small bit of light on the situation with the Sigma Delta Tau house since I am familiar with the investor that purchased the house from them. That happened about ten years ago, and they owned the house as a fraternity rental property up until maybe a year ago when they sold it to a fraternity.
I'll see if I can do some digging to find out if there are any houses still owned by sororities that are no longer there. One of my friends is a realtor who specializes in this area of town so she may know the answer. My gut tells me no since the real estate and property tax situations in west campus might make it difficult to hold onto a property for that long.