I recently got a fuck-up with them...
Tryied to send a box in Ontario (Im from Quebec).
It came back after about a week, saying that this adress is not existent.
Shipped it again, Expedite this time after having the adress confirmed with the receiving party and CP website.
It is on it's way back again, after I argued for a good 45 min with the guys/gals at CP.
They refunded me both shipping cost plus gave me a free shipping for the parcel anywhere in Canada. Ok. I had to force their lazy ass to check if the adress was valid using their own tools, and check that indeed there was some bill comming-in every month.
In the end, I only lost a lot of time.
Funny that they never send the parcel back the way it was sent... always the slowest/cheapest method. Even if it is their error.