1. The Liberals and the NDP are on the record opposing the Pickering airport project. Even assuming the Conservatives somehow wins back a majority in the next election cycle, Pickering won't be ready until 2035. So Pickering a moot point as far as Porter and Bombardier are concerned.
2. The chances of Porter operating the CSeries out of Pearson is slim to none. Pearson is very expensive and Porter will have to compete directly with Air Canada and Westjet. Plus even with the Union Express train they have no way to efficiently provide connections between YTZ and Pearson.
3. Porter could try to base the CSeries in other cities, such as Hamilton, or maybe even Montreal. But the business case for either option would be very shaky.
4. There is a reason Porter's CSeries LOI was converted into a conditional order. They can now just walk away from the deal, and they probably will.