how this 'relief line' ... is going to relieve congestion on the Yonge Line north of Bloor?
" It doesn't. For now it relieves Bloor Station (and to a lesser extent St. George), and Line 1 south of Bloor by providing Line 2 east passengers to another option to get downtown. This is by far a bigger priority than north capacity.Jeff Ranson on Facebook - May 25'17
Phase 2 is an extension north toward Don Mills, which should pull some off Line 1 north of Bloor. Phase 3 would presumably be a western leg to Dundas West or Keele that would further reduce transfer congestion at Bloor and St George.
Over capacity of the Northern part of Line 1 and the extension of Line 1 into Vaughan/Markham is a whole other issue."