It seems that wierd that TSN would say they would join the curling after the race, when there were 10 laps left, then switch to curling at 3 laps. Good way to irk all the fans. I know I tuned in at 8 pm for the curling, and did a WTF when I saw NASCAR and it was going delay the curling. I thought that it was dumb to show the race and delay the once a year final of an event that has had people watching all week.
I think TSN should have bit the bullet either way - either chop the NASCAR at 8 pm and carry the finish on TSN2 (if you get it) or wait the race out. When I saw curling coverage was delayed for 10 more laps, I tuned to a different channel and came back 10 minutes later and the curling was on. ie. The damage was done and switching at 3 laps was pretty moot.
IMHO the backlash was severe when the coverage was delayed and it was a seat of the pants decision to switch away at 3 laps.