The way government expenditure management actually works—and you're right that these are very complex projects—there are preliminary estimates based on plans, and then as plans firm up, you will actually be able to nail down, to a much greater extent, the costs.
At this stage, those projects involve things like engineering studies, relocation of utilities, and acquisition of the land that will be needed to put those in place. We're in the early days, for sure, and as time goes on, you'll see ways to actually nail down the costs to a much greater extent.
On some of its larger projects, the government does indeed have a practice of putting contingency funds in place, but when we talk about what's being voted by Parliament, it's the expected amount that will be spent during the fiscal year, so you won't see a contingency plan voted by Parliament unless it's needed for some reason.
What you're seeing here are the funds that those organizations plan on spending this year based on the planned work for the current fiscal year.