Take a look at the Lakeshore lines....has GO gotten anywhere close to off peak travel matching peak travel? The answer is no....
And does not need peak flows in offpeak in order to mathematically achieve the 400 percent.
Therefore, your statement, as worded, is thusly mathematically N/A even if your scepticism is possibly reasonable.
There are only 7 peak trains a day per direction. 15 minutes two way will do something like approximately 70-ish trains a day per direction, an
order of magnitude more train trips to Aurora. Not including any increased train rate at peak. And the 2020 increase is only partway, that 70 trains a day would be ~2025. This is Aurora+infills, not all the way to Barrie.
Do the math. 15 minutes is 4 trains an hour, times 17.5 hours a day, is 70 trains. 490 trains a week. The quoted 200 trains per week is what appears to be the half hourly scenario by 2020, that is not the 15 minute scenario by 2025.
Doesn't far more than half of Barrie commuters disembark at Aurora or south? Does anyone have a waterfall diagram of how many peak period disembarkations, for each station, for the evening peak? (Or hoardings in morning peak?)
The 400 percent increase is spread over ~1000 percent more train trips.
And we have not started talking about the infill stations which may almost double in number between Union and Aurora, in some scenarios.
Numbers exaggerated or unrealistic, maybe, but not nearly as much as you make it out to be, for a line that currently has no all-day-two-way service.
Easily 300%+ for 10x+ as many trains in a now-allday now-2way with infills. At this point, 400% isn't unobtainium today versus several years after 15min started.