Sure - -
http://static.nfl.com/static/content/public/static/html/careers/pdf/co_.pdf
1. There are a few exceptions that I didn't include in the above excerpt because they don't apply to the Bills - - you can see the full text including the exceptions at the link if you want.
2. Downtown Toronto is less than 75 miles from the nearest edge of the Buffalo city limits (as the crow flies) - - although I suppose it might be possible in the future for Toronto to build a stadium in the northeast suburbs that would be outside the Bills' "Home Territory" - - pretty sure the Rogers Center falls within the 75 mile limit, though.
Edit: After seeing the "radius map" supplied by Campy below, make that the Northwest suburbs.