Electrification doesn't effect it. steve munro wrote a good piece about it here:
http://stevemunro.ca/?p=5797
Essentially because of the layout of the tracks at (and before) Union, even if you do through lines it still takes 10 minutes to get in and out of union. (not 10 minutes spent on the platforms, but 10 minutes before another train can pull in) if you give each line 2 platforms, it is reduced to 5 minutes. But the problem with that is that we only have 14 platforms, but would need 19 for that scenario. Electrification really does nothing other than allow the trains to go in a hypothetical Lakeshore tunnel. GOs planned solution is to either:
i) build a new station at the bathurst yards for the Kitchener and Barrie lines
ii) build a lakeshore tunnel
each comes with it's detractors. The tunnel would cost $1.3 BILLION dollars to construct, but the Bathurst Yard station requires a transfer to a DRL that is really better off being routed away from the Rail tracks.
Both the Lakeshore electrification and the DRL (Probably not routing to the Bathurst yard) are going to be funded under the transit tax though, so I would expect the Lakeshore tunnel to be what they go with.