In both 1996 and 2008 the Canadian economy was hit with a big shock. The 1996 shock was the change in fiscal policy, turning a large deficit into a large surplus. The 2008 shock was the global financial crisis. (Canada didn't really have much of a financial crisis; no banks failed, as usual.)
In both 1996 and 2008, the Bank of Canada kept inflation (more or less) at the 2% target (in 2008 total inflation fluctuated above and below target, but core inflation stayed close to trend).
In 1996 there was no recession. In 2008 there was a recession. Why? (I don't have an answer to that question, sorry.)
In my view, the main thing we are looking for when we choose a monetary policy target is that it prevents recessions. Inflation targeting passed that test in 1996, but failed that test in 2008. I used to be a supporter of inflation targeting, because it seemed to work well in practice. When it became clear to me that inflation targeting had failed in 2008, I stopped supporting inflation targeting, and switched to supporting NGDP level-path targeting.
But I would feel a lot more confident in my support of NGDP targeting if I understood why inflation targeting worked in 1996 but failed in 2008.
Worthwhile Canadian Initiative 
Nick:
I didn’t really mean to ask specifically why not a PLT, I was just trying to point out that I think NGDPLT seems to be arbitrary without having a specific model behind it. IT and PLT have NK theory, the Friedman rule has frictionless models where there is an opportunity cost to holding money, what model or class of models says that an NGDPLT is optimal and/or significantly better than IT or PLT?
John: “…what model or class of models says that an NGDPLT is optimal and/or significantly better than IT or PLT? ”
Here is my tentative sketch of an answer
But NGDPLT will never be exactly optimal, unless you rig all the parameter values to make it exactly optimal.
In 1996 there was no recession because global growth (especially USA) was strong.
In 2008 there was a recession because global growth (especially USA) was weak/negative.