Dredging Burrard Inlet should be much easier to miantain than doing so for the St Lawrence as I suspect the sediment load to be much less.
The St. Lawrence Seaway has never lived up to traffic projections and seems to be declining.
The dream of significantly greater European trade will remain forever a leftist fantasy. Besides slow growth, Europe is not a great market for anything other than raw materials. It suffers declining competitiveness for manufactured good, so why would it import from another uncompetitive manufacturing nation like Canada? The resources for which it would have greatest demand would be those historically provided by Russia: oil, natural gas and grain. Unfortunately all of those are located geographically and politically on the wrong side of Canada. The US is much better prepared to replace Russia as it produces those resources on the Atlantic Basin. Economics also wins, so the notion that Europe would prefer trade with Canada as Trump offends its sensibilities is nonsense. The inconvenient truth is that Canada's future lies with Asia in spite of Laurentian preference.
What about the Port of St. John. Does it have the road and rail connections to pick up traffic from Montreal and Quebec City?