Is there a track map showing where crossovers are located?... Or, half of OL trains can short-turn at the Exhibition to provide capacity for the transfers from GO, but then the western extension will be limited to half the capacity.
I would expect tat there would be crossovers next to East Harbour so that OL trains could short-turn in the east (as well as at Exhibition in the west) so they can run a "GO to downtown" shuttle.
It needn't be half the trains.
They could do it as 1 or 2 trains that are interlined with regular service just to relieve the load.