just to preface, i won't post again here but i really don't know. i have some idea and then i'm googling the rest.
http://madanca.com/blog/taxation-of-...ees-in-canada/
it looks like exercising the option is the taxable event. and this article explicitly says the tax can not be deferred.
if you are fine paying a small amount of tax (say $3000 or $5000) and you believe in the company then "go for it"
if it's a meaningful number relative to your financial circumstances, i would sell the stock to at least pay the taxes. i would not take a loan to pay the tax.......
one thing i would mention is that it seems like every single canadian high flying stock dies a very violent near-death (laidlaw, loewen, newcourt, valeant, nortel, black berry). and i think general financial market conditions are nowhere near as good as they were when those aforementioned companies soared.
and just to repeat, make sure you understand that your stock option income is basic income, you stock gain/loss on holding the stock is capital (a loss being nowhere near as good). they don't offset, even in separate years.