Yes, because right now, if you bought those 100 shares—let's say, for the sake of argument, they cost $200—and you paid $100 off your paycheque to buy those shares and WestJet contributed $100 in shares to you, then you would immediately have to pay tax on the $100 in shares that WestJet bought for you.
On December 4th, 2007. See this statement in context.