But weekday service on those lines is rush hour only. This may be limited, but it's well defined and people know those trains are going to run. Weekends are a bigger problem, and a limited service model much much harder to make work. If you say that are going to run trains for the Jays, terrific - but now you have trains running some hours and not others. That kind of variability will lead to people not taking the trains because they don't know when they will be available, particularly since potential riders' weekend trips are MUCH more varied in scheduling. Some go downtown for work, some for shopping, some for clubbing, some for sports, etc - and ALL of these groups have different travel times for the other groups.
I'm not against the idea itself but I really don't see how any "irregular" service is workable outside of the rush hour trips where people travel at the same time five days a week.
No, the next logical step is to add hourly all-day service, covering the three time periods (midday, evening, and weekend). Not all periods need to be introduced at once, but once a period is introduced riders need to know that the trains will be running every hour during that time period, without any scheduled exceptions.
And this is exactly what GO has done on Lakeshore, so it seems very reasonable to assume that the model will be transferred to other lines.