Some additional thoughts:
1. The news today that Algoma Central Marine has acquired the Panamax self-unloader Gypsum Integrity to run under Canadian flag as Algoma Integrity on the iron ore shuttle from Port-Cartier to Contrecouer, QC puts some more logic behind the move to add a third tug in Port-Cartier. That ship will be in and out of port weekly year round, ad due to its size 197m loa and 32.2m broad, it will certainly take two tugs to berth.
2. I notice the crew on Svitzer Cartier are all wearing bright shiny new Svitzer hard hats and coveralls. The skipper, when the tug came alongside yesterday after fueling, was very adept at handling the tug, and where would be get that experience? Obviously not a new hire, despite the fresh coveralls. I'm guessing Svitzer Canada has taken over management of the other tugs in Port-Cartier too. It would only make sense, since up until now the tugs have been managed by the iron ore company itself (now ArcelorMittal, but previously Quebec-Cartier), and why would they want a third tug under a different management arrangement?
3. All that raises the third supposition. With Svitzer on board, and access to a world wide network of tug operations, and faced with eventual replacement of the two incumbent tugs Brochu and Vachon, could we expect an announcement of some more new tugs soon?
The new Svitzer Cartier has two sister tugs recently "blacked" by Australian unions due to an asbestos scare, but my guess is that brand new tugs are more likely. Brochu and Vachon are reported to be in excellent condition, so there is no rush, but inevitably more powerful tugs are in the cards.