My mistake. You are correctThe cancellation of the Man U match has nothing to do with TSN2. They always had Chelsea v Everton scheduled (there was no 12:45 UK kickoff scheduled for this round).
The Blackpool v Man U match was slated for 17:30 UK kickoff which is the timeslot belonging to Sportsnet-1.
Sportsnet-1 has just announced that they will be showing Wigan v Stoke City (2-hour delay @ 12:00pm).