It is because Ontario is bleeding money out their back end. The manufacturing jobs have all left the province and with Research in Motion about the cave (Blackberry) another industry is about to leave the province.
The government is doing whatever it can to attract more business to the province.. even if it means parasatizing from other provinces.
Rockstar made a big mistake. By consolidating its ops into one province for a short term tax incentive they are no longer as diversified. By joining a sinking ship and putting all their eggs into 1 provincial basket they have effectively screwed themselves.
They will be closing their doors soon. It is unfortunate.