Dont know how you define the term "some problems", but CN has been experiencing 10-15 derailments a year on former BC Rail trackage, most if not all directly related to trying to force CN train handling procedures on the twisting, not-always-smooth and steep BC Rail track profile. Stringlining, break-in-twos and rolling the rails over have seemed to comprise most of the causes, and it took a runaway of a one-car and one-locomotive train recently (which killed the CN brakeman trying to turn the handbrake of the one lumber car at speed in a last ditch desperate move to slow the train, he wound up dying as the car went over a embankment) to force Transport Canada to issue a edict to CN to only operate dynamic-brake equipment on BC Rail north of Vancouver (the solo GP40-2LW was not dynamic brake equipped).

Just my opinion, but when you keep derailing trains due to train handling over and over and over AND over on the very same stretch of rail, at some point youd think youd learn that as a railroad that what works in one area of the country doesnt always work for all. CN has proved beyond all doubt that theyre not interested in learning this lesson.