I use the Greater Golden Horseshoe definition, which is not only "MapArt's Toronto and Area Atlas" but also Hamilton, the Regions of Niagara and Waterloo and the Counties of Wellington, Peterborough, Northumberland, Brant, and Victoria.
Thanks for the link. It looks like Barrie's obliberating the rail bed of the CN Newmarket Sub, unfortunately. But Allandale redevelopment looks like it might compensate for that nicely. The hotel/conference centre looks interesting, as does the old IGA and Lakeview dairy sites.