what are the unique factor that define the need for these two subway extensions....what is unique (as was suggested in the first post I replied to) about York's geography or targets that means they can only be achieved with a subway while a lot of these other Urban Growth Centres will never (should never ) see a subway but are expected to achieve the growth targets set for their UGC?
This has been discussed ad nauseum on the Yonge Subway thread and I'm loathe to go on about it at length again. Here's the (second) short answers/elaborations:
-First, you're making a fundamental error: As I said, the targets are MINIMUMS. So everyone has to meet them but, as work by Neptis has shown, the vast majority of GGH municipalities have treated the MINIMUMS as MAXIMUMS. Which is to say, almost no one except Markham, Vaughan and Waterloo have set their 2031 intensification targets above 40%. Downtown and Yonge/Eg are the only existing UGCs above their density targets.
So, if you're asking whether they can hit the target in Markham or Vaughan with less infrastructure, the answer is "probably, sure."
But if you want them to EXCEED the target, they will obviously require more.
Making that investment, hoping a subway will lead to a large-scale, urban TOD in (for example) St. Catherines, is obviously silly.
You do it where it makes sense geographically (ie just outside Toronto, where direct connections to its network are) and where you have a municipality that is not only amenable to intensification but willing to go the extra mile.
If all you want to see is every municipality creep up to the minimums, by all means, nickle and dime them. Or you can realize there are 25 UGCs but they're not all created equal.
-Again, proximity to Toronto: Not one of the other UGCs is so close to Toronto and particularly not along a contiguous urban corridor. Which is to say, intensification is already continuous along Yonge from the 401 north. You would be constraining the natural market forces if you didn't maximize the infrastructure which, by the way, is a key policy in the Provincial Policy Statement.
-In the case of the Langstaff UGC (as I've explained several times, often to people who don't quite get it), there are major constraints as there is only one road in and out. So, when the Secondary Plan was developed, after YNSE was proposed, they worked backwards from the assumption the transit would bear the brunt of the transportation capacity and the road very little. This is the opposite of how developments are typically planned. The density and population figures were then reverse-engineered from the capacities of the various modes (YRT, Viva, GO, Transitway, Subway) converging at the site.
Ergo, you could swap in an LRT or even a BRT but it would - and this is explicitly spelled out in the Secondary Plan - lead to a lowering of densities and population/job targets. So the subway is hardwired into the planning.
-This is not true of VMC. the subway there "makes sense" because it already made sense to go to nearby York U and then the 407, where the province (allegedly) plans to run an east-west regional BRT. I'd be happy to agree that, unlike Markham and RH, Vaughan has not maximized the potential a subway offers in its planning targets but it's also early days. And the larger principle about doubling down where and when you can still stands.
That's my honest answer to the honest questions.