If you want to watch The CW’s Arrowverse crossover event on Canadian channels, here is the schedule for Ontario. All shows will be at their regular times and will match The CW, except Arrow will be on a special day and will be one hour later than The CW.
Supergirl - Monday, Nov. 27 at 8 PM (Showcase)
Arrow - 10 PM (CTV Two) following the two-hour episode of The Voice.
The Flash - Tuesday, Nov. 28 at 8 PM (CTV)
Legends of Tomorrow 9 PM (CTV Two)
It appears the crossover episode of Arrow will not be shown on SPACE. Note that the episode of Arrow titled "Thanksgiving" (S06, E07) that precedes the crossover will air on The CW and SPACE on Thursday, Nov. 23 and presumably on CTV Two on Wednesday, Nov. 29. I doubt that there is any disadvantage to watching that episode out of sequence on CTV Two, since the crossover will have a separate story arc. All info is based on Zap2it listings.