On the topic of York Region's stance on how the extension will manage over-capacity...
I've already stated countless times that if the extension is made, the TTC intends to turn back an empty train at Finch station. This alone would help alleviate a huge burden on the other stations further south down the line that are currently reaching capacity because it will mean a fresh train for the riders to hop on; something that they currently cannot do with the current system.
Not only will less people flood to Finch station (meaning if they decide to turn back at Finch but still allow riders to hop on at that station, it would still mean a huge decrease in riders at that stop), it would mean that instead of waiting for 2 or 3 trains to pass before they can maybe sneak onto a train, they'd only have to wait a maximum of one train... if that.
So every time I hear the whining about the capacity of the existing stations being overloaded being used as an excuse to not build the extension, I cringe. Just another bunch of selfish anti-growth dramatics.