Covering Grafton is my one big worry about this project. Turning streets into underground spaces rarely works out. The Philadelphia example is a good demonstration of the pitfalls! In Calgary, 3rd Street Southwest has been covered over by the Eaton/TD Centre and all that keeps it from being truly awful is that it's mercifully short. It's always so much darker and dingier in there. It really makes for a hostile streetscape.
Calgary
The original plan to have a much more airier Grafton by putting the convention centre space underground was probably better.