You are saying $2b to electrify, add rolling stock (how much?), and add four new stations (including physical integration at Leslie/Oriole, adding one at Eglinton, and maybe doing something at Finch)?To electrify the line, we are looking at $5m/km for 2 tracks that inculdes substations.
To upgrade the RH line itself, $850m including grade separation. This also includes 4 new stations.
Rolling stock using EMU $200m
Therefore, far cheaper to upgrade the RH even if it cost an extra Billion to fix the line to have 3 tracks than to build a new Yonge subway.