I wonder if the deal struck with CN to deal with Brampton and Silver Junction will provide a template for addressing Niagara service. From a capital perspective, clearly Metrolinx is struggling to find current projects, so it is likely waiting a few years. But the big things to address would be:
-A third track and upgrading crossings through Hamilton to increase speeds. Grade separations would be nice, but crossing upgrades should allow speeds up to 60mph I believe.
-Double tracking and speed upgrades on the Grimsby sub out to St. Catherine's. The corridor is wide enough and straight enough for 90mph track and either double track or passing sidings to allow for up to 30 minute bi-directional service while still dealing with some freight operations.
Bayview junction will need upgrades to prove service beyond 30min, and at some point the Welland canal bridge will need to be addressed, but those should wait until speed upgrades are done.