As you note, they allow that at the rural terminals, like Duke Point and Tsawassan, not certain they do at the more urban ones.
Have you checked with the BC Ferry folk (ya, I know getting an answer can be.....)
2008 F350SD V10 with an 2012 Arctic Fox 29-5E
When someone tells you to buy the same rig they own, listen, they might be right. When they tell you to buy a different rig then they own, really pay attention, they probably know something you don't.