At the risk of being thought "cavalier", I don't like what Bank of Canada governor Stephen Poloz is reported as saying by Kevin Carmichael.
Inflation targeting is supposed to be inflation forecast targeting. The Bank of Canada is supposed to do what is needed to ensure that its own internal forecast of future inflation (at a roughly 2-year horizon), conditional on the Bank's information, remains at the 2% target.
Inflation targeting is supposed to be symmetric. The Bank is supposed to respond to new information about any shock to Aggregate Demand to prevent that shock affecting its forecast of inflation, whether that shock is positive or negative.
The Bank of Canada is not supposed to follow any simple instrument rule, like a Taylor Rule, if that simple rule leaves out any information that might be relevant for the Bank's internal inflation forecast. For example, the only information in the Taylor Rule is the output gap (the difference between current output and potential output) and the inflation gap (the difference between current inflation and target inflation). Using a Taylor Rule implies ignoring any information the Bank of Canada might have about shocks to the natural rate of interest. [I say this notwithstanding the internal inconsistency, like the Cretan Liar Paradox, of the Bank's own Totem model assuming that its own future actions will follow a slightly-modified Taylor Rule.]
The whole point of inflation forecast targeting is that the Bank of Canada does not "accommodate" any shock to Aggregate Demand that would change its internal forecast of future output and hence future inflation. And that includes fiscal policy shocks. The Bank of Canada is supposed to offset any such shock, 100%. It makes no sense for the Bank of Canada to provide any estimate of fiscal policy "multipliers" other than zero. Even calculating a hypothetical "multiplier", for how output would respond if the Bank did "nothing", makes no sense, because the definition of "doing nothing" is arbitrary. Even if we agree that "doing nothing" means "doing nothing with the nominal rate of interest", that leaves open the question of how long the Bank holds the nominal rate of interest constant. And "forever" is not a meaningful answer to that question, because standard New Keynesian models (and the Bank is New Keynesian) tell us that monetary systems will either explode or implode if the central bank holds the nominal interest rate constant forever. [The Bank says it does accommodate the "first-round effect" of short-run supply-side or price shocks, like changes in indirect taxes, but that's not what we are arguing about here.]