Torontonians are rather short sighted to not care about the Yonge extension just because some of it goes beyond our border. Why is it that some people don't see the benefit of removing thousands of buses a day off of Yonge St, improving the insane traffic at Yonge & Steeles, redeveloping all those ugly strip malls north of Finch, shortening several bus routes, and providing Toronto residents a faster commute to their jobs in York Region so that they don't have to move out of the city? This whole self-centred Toronto parochialism is not helping anyone, and it needs to stop.
Some of this seems a bit fallacious, because your argument can be construed to the point that you're claiming Torontonians who oppose a Line 1 extension to Yonge/Hwy 7 don't support high-density development, transit expansion, improving commuting times, improving access to jobs, improving traffic... I think that couldn't be farther from the truth, and I doubt there's a single member on this site that doesn't support these things or improvements to the Yonge corridor.
The issue many have with sending a subway north of Steeles is mostly cost ($4,600,000,000 last TTC estimate), and whether this is warranted. That's a lot of money, and we have a lot of longstanding priorities that are unmet - many predating the Big Move by decades. Current surface ridership along the Yonge corridor north of Steeles is what, the 30th busiest? Or somewhere in the mid-high twenties? Sure that's a lot, and is definitely worthy of infrastructure to improve the current situation of an armada of buses. But is it really worthy of a $700M/km investment?
Another point is politics. Sorbara's autobiography somewhat admitted an extension to VMC was a porkbarrel of sorts. How do we know this is any different. And why is it that the Richmond Hill GO line got downgraded from an Express Rail promise to seeing next to no improvements. Was it to improve the business case of Yonge North? It had 29min RHC to Union express service, an excellent business case, would've detracted significantly from subway ridership (particularly with Mlinx's proposed fare structure). So was this downgrade a sacrifice worth making?
Another point is development, and whether the claims of highrise office/residential development at RHC/LG - with ultra-high transit mode shares - will pan out. Not to sound like a negative nancy, but we have decades of well-documented evidence that shows how suburban "Centres" never really develop as promised. With numerous factors that can affect this. We even have a current case in point to follow: VMC. It has half the proposed density target of RHC/LG, no NIMBYs for over a mile, and it seems to me they're nowhere near making their 2031 target - all this in a market that's perfectly conducive to urban office and residential development. They'd have to add thousands of residents and office jobs each year for the next fifteen years to meet the promised density goal, and I don't see that happening. And Markham Centre, even with the recent upgrade from AD2W using diesels to electrified RER (and 5min TTC fare SmartTrack) would see inbound 470 and 812peak...so little ridership, for such a massive suburban job hub?
Another point is whether other transit modes were overlooked during the Big Move promise (e.g something between BRT/LRT and subways). I know that Vaughan is currently supporting a 6km subway extension to Wonderland and VMC2 (Vaughan
Mills Centre) in place of Viva Silver, and YR's TMP is studying bringing Line all the way up to Major Mack to create a belt line loop. But to me this seems absurd. Not because I don't support transit expansion and subway-like railed RT across the region. But because the mode (heavy rail subway) is too damn costly. Yonge is a massive highway-like arterial, and I think light metro / advanced light rail would be the most optimal mode for YR's future (no, not an in-median BRT/LRT...I mean a true medium capacity subway-like system). The roadway allowance is more than ample to handle a well-landscaped guideway, and in other areas like Thornhill the line can be underground or trenched. Its speed/reliability is on par or above subways, and depending on how it's designed the capacity can be damn near close a 6-car TR. IOW, it's the exact same as a subway, but you get 3-4x the coverage for the same price.
I get that people will be ready to toss out insults, or post disingenuous images of 30s-era Chicago ELs, or defunct monorails, or theme park rides. But if you take a trip to Vancouver or London, you can save yourself the trouble. So rather than wait a century and untold $Billions for a piecemeal subway extensions that may never materialize, or rely TO City Hall to consider it - I think YR would be wise to plan for, design, fund, and operate a light metro themselves. They call the shots. And this one arcing line from Jane / Major Mack / Yonge would be a perfect mirror of Line 1.