Not directly Bypass related but it is a key priority project for CN Rail on the Halton Sub.
Halton launches legal action to gain control over rail project
Improve the Halton Sub to the point where GO can run trains from Aldershot to Bramalea and you have a deal. I'm thinking specifically as part of a future "ring" line (up the Halton Sub, across the York Sub, and then connecting back to the Lakeshore East line at Pickering), having the Halton Sub upgraded could be beneficial. This would also potentially provide Hamilton/Niagara/Burlington with a direct connection to Pearson if such a routing were ever approved.