Are you talking about 419 Dundas Street East?
It's been for sale for ages, the sign even appears on Google maps!
"Prime Downtown Development Site....In The Revitalized Regent Park Area.
This Land Won't Be Available At This Price For Long! Mixed Use Commercial Residential, Great For Live/Work Space **** EXTRAS **** Zoned Mixed Commercial Residential 1.5 Times Coverage. PerfectFor Main Floor Commercial And 2 Floors Residential. " 16.83x114.00 FT
Alternately, you could be talking about 423-427 Dundas St East, which will be (was to be?) the site of an aboriginal rooming house (info:
http://www.cabbagetownsouth.ca/Default.aspx?pageId=897452 ).