^one thing to add to this:
I have heard on good authority that the city is being quite conservative with time estimates (as mentioned) and also, the phasing of the project is up to the contractor. The Valley Line SE was built all at once, but the West might not be. Not knowing much about this World Cup Bid (i don't follow sports sorry) so not knowing the venues, it is conceiveable that the line is built in sections from say, DT to 149, 149 to West Ed, and West Ed to Lewis Estates is completed last. This could improve the timeline for the event as well. IDK, i am speculating here about how phasing could work, but i do know that the city is allowing contractors to plan that aspect, and is not ruling out building section by section if the logistics are better.