Take a look at City Planning's Zoning By-law map:
http://www1.toronto.ca/city_of_toro...ent/files/pdf/city-wide_allzones_569-2013.pdf
On the south side of the York Mills and Lesmill area, just about all of that area is zoned for industrial.
On the north side, a relatively small area has been zoned for industrial employment lands. The rest shows no zoning information. So it's possible that any redevelopment would be limited to the north side, which would still make for a very large scale redevelopment (about 175 acres vs. the 295 acre that I originally proposed).
However, I'm not certain how the province goes about designating what is industrial lands. Would they determine that solely on the zoning by laws for the area (as shown in the aforementioned map), or would they base it on the actual land use of the area?
Looking at street view images of the area, it appears that the north side is mainly commercial business parks. Hopefully this would make it eligible for redevelopment.