The For Dummies version:
Because here's the thing: Even though we now have a fixed election law, it isn't completely binding on the government that adopted it.
The For Non-Dummies version:
1) The revised Act will NOT let a government that is down in the polls extend its term into a fifth year, a la Mulroney's gang and Bob Rae's hapless Ontario Dippers.
2) The revised act WILL continue to allow a government up in the polls to pull the plug on a parliamentary section and call a snap election, a la Chretien in 2003.
The question really has only ever been will the Tories, having touted Bill C-16, pay a price when and if they try and slip out through one of its loop-holes? Hard to say. If the first week of any election campaign can be made to be about the timing of the election call, then maybe. Think David Peterson.
By the way, Ted at Cerberus wrote about the defects of this Bill C-16 back in May/June of 2006. The MSM is just now catching up, apparently.