There are myriad issues in this thread.
I'm sure I've contributed thoughts before, but will restate and contemporize them here.
On whether the extension should be built:
This is a legitimate debate, and it does not service the cause of good policy to have extremists at either end playing fast and loose w/the facts.
Steve Munro, who has expressed a clear preference for the LRT/Transit City version has conceded there are merits in going with a subway extension, although it would
clearly not be his first choice, and the express version of the line, in combination w/Smart Track makes a so/so case worse.
Let's break this down shall we.
In Favour of the line:
The number one argument is simply that reconstruction/replacement is necessary (of the current SRT) and that replacing the lost capacity during a closure of 2-3.5 years would be very challenging and likely inconvenient for existing riders.
Two, the current line is over capacity, so we know, as there is a parallel bus service that there is not only greater demand that what the SRT serves, but to a near certainty, latent demand as yet untapped.
Three, the oft-cited comparison in passenger volumes of demand for a subway are disingenuous in so far as no line's volume is measured based on that at its outermost stations, which will by definition have lower volume.
The traffic numbers, by global standards, and even more so, North American ones aren't unreasonable, though they do skew to the low side.
Four, if built w/additional stations, there may be opportunity for greater/easier access to a major hospital (trip generator) and possibly the removal or reduction of some bus services providing a partial operating offset.
Five, by historic standards, volumes will be much higher than outer reaches of the B-D line when first built.
****
Against the line:
As proposed, it has only one station added.
This means many existing riders will be inconvenienced, ridership will be lower than in versions w/more stations, there is unlikely to be any material benefit in terms of bus service reduction/removal.
The line is more expensive than originally stated, and more expensive by some measure than the LRT option.
It will serve fewer people in terms of direct access than the full LRT to Malvern version in terms of catchment area.
It therefore serves fewer vulnerable, low-income folks as well.
The current version w/only one station just doesn't make sense, the speed of operation benefits are negligible and it the costs savings are partially offset by the need for additional emergency exits.
****
Clouding the debate
Figures are fudged and misrepresented by both sides
Cost figures are altered by 'yard accommodation costs'
In the case of the above, the yard for LRT has been cancelled and its costs were tied in w/Sheppard LRT which itself has an future TBD.
While the subway yard capacity required to serve an SSE has now been purchased, and will likely be built out regardless to serve a DRL.
Its an open question as to what portion of those costs should then be charged to the SSE project.
The line makes more sense w/o Smart Track at Lawrence.
Smart Track @ Lawrence can't co-exist w/the LRT option anyway, so far as I understand.
Finally, Scarborough General Hospital is the main argument to me for choosing an SSE (obviously contingent on a station to serve it).
Said campus will be rebuilt, w/in 15 years, the only question is whether that will occur at the current location.
If it does not, the rationale for the SSE crumbles, in my mind; if it does, the rationale is likely enhanced, as I expect a replacement hospital to be materially larger, w/higher patient volumes, visitors and employment levels.
********
My 2 cents, the argument for the SSE is sound, subject to including 2 additional stations, removing/reducing select bus services, no Smart Track @ Lawrence, and yard accommodation costs being pro-rated to the capacity required for the extension. The further fiat being the upside cost is hard capped at 4B.
That said, an LRT alternative is a legitimate choice; and the preferred choice if the hospital is relocated, or the SSE built in non-viable fashion.
***
The Final Word: The Relief Line is a much higher priority than either of these projects, give or take the SRT's expiry date.