I was also able to volunteer at Union Station for Doors Open. I think typically they have done tours through the building in previous Doors Open years but it was self-exploration of the building which included an art installation in the West Wing. There was also a video available on a 9-minute loop that provided information on which movies were partially filmed at Union Station. One of the more recent movies that filmed some scenes at Union Station was Amelia.
The stores and restaurants in the retail portion of York Concourse were open and available to pop into if they were open on Sunday morning. Union Station did provide some history in their art installation alongside the information available on the future of Union Station.
The one new thing I learned about the station was that they now scheduled drawing classes, Union Draws, on the last Sunday of the month. The classes are for all skill level and are taught by a OCAD teacher.