I believe that the exhibit was some 20 years ago. The model was to be disposed of and a railroad historian rescued it before that happened. The model had been in stored in a non-climate controlled location until this past spring when I went to collect most of it for a partial restoration of various elements.
Yes, at O Scale it would be huge. The base for the HO Scale 7th Avenue facade is 72" wide. It is my understanding that the model was 6' wide by 12' long with extensions on both ends to create loops for trains to run through the station area. Make that O Scale and we're talking nominally 12' by 24'! I have the Hagley plans and access to the original drawings. Who's game?!
What struck me about the contents of the exhibit that I have seen were the photographs of the original station. They had many panels with photographs that I had never seen.