I'm wondering if the flyover they recently announced west of Georgetown would still be necessary if the 407 freight bypass had been constructed. The bypass would eliminate the conflict point between CN and GO west of Georgetown, probably making the flyover no longer necessary.
I'd go with a freight bypass isn't necessary with a flyover.
A bypass would have been astronomically more expensive. The rail overpass for that might (or might not) have been a bit cheaper - but not that much cheaper. And there's a huge cost to grade the rest of it.
And how many new overpasses? Bramalea Road, Dixie Road, Tomken Road, 410 (probably 8 overpasses with the massive interchange), Kennedy, Hurontario, McLaughlin, Mavis, Financial, Mississauga, Heritage, Winston Churchill, Ninth Line ... the 407 ... and where then? Along the CP alignment, widening several more structures?
Metrolinx estimated that the bypass would require 35 new bridges, the relocation of 17 hydro towers, and 30-km of new rail alignment. The 2015 estimate to both CN and CP was $5 billion, and surely it would be similar now even if was only CN.
I really don't know why there was any discussion of the bypass after that report came out, if the flyover fixed the issues, much more cheaply.