Why not just tunnel (with a shield) east from the ends of the subway platforms adjacent to the running tunnels until under the Metrolinx RoW and *then* put an elevator and stairway(s) up to the existing Bloor West tunnels? It will make the ticket barriers a bit more involved than the previous concept, but be far easier in the long-run, not least because beside having to be signed-off by engineers and authorities, it doesn't need the co-operation or permission from Crossways.
Might there be unexpected complications? Doubtless, so will there be opening up the basement of Crossways and doing the connection as now conceived. Tunneling might in fact be the lesser challenge, and far less disruptive and expensive in the long term. Sections might have to be daylighted and cut-and-covered (retail outlets and stairways, for instance) but this form of connection works very well and has for well over a century in cities like London, New York and others.
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