When does the tax come into effect?
In the meantime, consider this; when Que had their last referendum, CP Rail relocated the HQ along with 2500 jobs from Montreal to Calgary. Ever wonder why the chose AB as opposed to more obvious hubs like Toronto, Vancouver or Winnipeg?
If you have to move anyway, then you'll look for the best location economically. But if you don't have to move, you might just bear the tax increase as long as it's reasonable. Also, consider the difference between an impersonal corporation and an indivedual rich person. The person may have family attachments or friends in the local community, so there can be an emotional attachment.
Now just for the record, I support eliminating all corporate income taxes and instead just introduce co-determination legislation to ensure the money does in fact flow down.