Tolling has two primary purposes: to generate revenue, and to encourage mode shift. Tolling now would be very effective for #1, but would be a pain for #2.
Prior to COVID, GO was operating pretty much packed to the gills during peak periods. Unfortunately for GO, options to increase capacity by increasing frequency are very limited without first investing in necessary track upgrades to remove pinch points or remove conflicts with freight. A lot of those projects are funded at this point, but are still a ways away from becoming reality, or are under construction (see: Stouffville Line double tracking, Barrie Line double tracking, Barrie Line viaduct, Stouffville-Lakeshore fly-under, LSE 3rd track from Guildwood to Pickering, etc).
With the GO system still operating at its maximum theoretical frequency on many parts of the system, adding the necessary capacity to handle the mode shifters that tolling would generate is a tall order. This is especially true for the Gardiner, which serves many coming from Mississauga. The Milton Line in particular would need billions in investment to make it a viable AD2W alternative to driving. Even during peak, there isn't much room to handle the natural increases in GO ridership due to population increases, let alone the spike that would happen if tolling were to be implemented.
TLDR: Tolling is good, but you need to make sure that the modes that people will shift to have the capacity to handle them.
Prior to COVID, GO was operating pretty much packed to the gills during peak periods. Unfortunately for GO, options to increase capacity by increasing frequency are very limited without first investing in necessary track upgrades to remove pinch points or remove conflicts with freight. A lot of those projects are funded at this point, but are still a ways away from becoming reality, or are under construction (see: Stouffville Line double tracking, Barrie Line double tracking, Barrie Line viaduct, Stouffville-Lakeshore fly-under, LSE 3rd track from Guildwood to Pickering, etc).
With the GO system still operating at its maximum theoretical frequency on many parts of the system, adding the necessary capacity to handle the mode shifters that tolling would generate is a tall order. This is especially true for the Gardiner, which serves many coming from Mississauga. The Milton Line in particular would need billions in investment to make it a viable AD2W alternative to driving. Even during peak, there isn't much room to handle the natural increases in GO ridership due to population increases, let alone the spike that would happen if tolling were to be implemented.
TLDR: Tolling is good, but you need to make sure that the modes that people will shift to have the capacity to handle them.