There are other 'issues' that make make the R-H line a fairly low priority; though it needs to be said, the Portlands plan will not eliminate upstream flooding of the rail corridor; though should reduce it some.
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Aside from the circuitous route of the line and difficulties in adding stations anywhere south of Don Mills just north of Lawrence, there is the serious problem of Pottery Road.
Frequent, all-day, 2-way GO service would require grade separation of Pottery Rd.
You can't go down due to flooding issues, which means the rail corridor would have to go over Pottery, given the need for a relatively gentle grade, this impacts a huge length of track, and in the middle of an ESA no less.
To my knowledge, there are no detail designs or good class estimates of cost, but there is a back-of-the-envelope examination around somewhere and the costs were exorbitant.
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I know a bit more than that, but what I can tell you is there are no plans to significantly ramp up service on the existing track, at the existing grade.
And, no, don't expect any near-term projects for a massive grade separation or other alternate scheme. In the longer term.......