I would argue that the most cost-effective shorter term action would be to infill an Eglinton-Brimley station on the SSE to which Eglinton East buses would be routed. This would shave ~1.5km off the current trip, skip traffic lights at Midland and Brimley, and maybe Danforth too depending on how you orient the at-grade station/terminal; and would easily shave 4M+ off the current route. All for ~250M; a far cry from 4.4B ++
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In the longer term, I think a Line 4 extension from McCowan to Markham, which then goes south to Centennial's progress campus, and then west to Neilson, where a single, straight, short bus (or LRT) run can connect the line to Malvern to the north and Scarborough Centenary Hospital to the south, and then on to UTSC.
Its a ~6km subway extension, with 4 stations. should be able to come in for about 8B (today's money) add Neilson LRT (if so desired) with ~4km length and you 're al in for maybe 10B Just over double what the EELRT is budgeted for; but with, I would argue, a vastly better pay off.