Just out of interest I overlaid the McMahon Stadium in Calgary on the DND lands north of the Halifax Forum (based on Google Earth images at the same resolution). It appears as though the only way to fit a stadium on these lands would be to go with a significantly smaller stadium than McMahon Stadium. If the second tier of seats were removed then it might just barely squeeze onto this area without going past the supermarket. I will try it on a few other areas (Dartmouth Crossings, Mainland Commons and Shannon Park) some other time.
Here it is:
