Ellen’s info is perfect, and what I’m about to write will be inferior. Sorry about that.
Ship movements are monitored and controlled by Vessel Traffic Services – there are 2 main centres – Victoria and Pr Rupert, but they operate using remotely-controlled local transmitters using various frequencies, which are not so easy to determine. For the Vancouver area Ch 12, is the one to listen to, and in the Gulf Is it is Ch 11. You can listen in to help to decide when a big vessel might be coming by, but then you would need some idea of that vessel’s speed and heading, which are not given. Also those vessels which are not required to call in (but might also be big and/or fast) will be missing entirely, so it is doubtful how valuable this would be to us kayakers. That said, I have called VTS on a hand-held radio a couple of times, to find out in poor visibility what ship movements were known in that area and also to warn them that kayakers were about to attempting a crossing, where there might be a possibility of collision (although wipe-out would be the more correct term, since the ship’s crew would never known that it hit us). VTS seemed quite willing to transmit a warning about potential traffic conflicts even involving paddlers, but I would not do this routinely for fear of being considered a nuisance. It is best to not make those kind of hazardous crossings! Still, it can be useful to know that no BC Ferry is due down a particular channel for another 2 hours or whatever, so it can help with the timing of some channel crossings.
Having access to AIS info on a mobile phone app might be more useful overall, however!