So it is likely that the sign referes to a pticular grade of Salt Cod, rather then to where the fish was caught as it seems unlikely that this fish actually came from the Grand Banks. Maybe.

Yes, maybe.
I have never seen a grade of salt cod here, labelled "Labrador". What I do find, is (1) large skateboard cod, requiring a lot of soaking, in many ethnic stores, such as Caribbean or Portuguese, or Spanish; (2) A softer, boneless cod, packed in poly wrap, usually from Nova Scotia, but still "Grand Banks" though the fishery is banned within our 200 mile limit. Labrador is within the limit, as well, but there is a lot of rule breaking, by Canadian and foreign trawlers.
I buy the softer version because it freshens easily. I have been served bacala and cod with ackee in Portuguese and Caribbean restaurants in Toronto that was too salty for me. And too bony, but this is a matter of taste, and culture.
For those on a budget, salt cured pollack is available, but doesn't have the same taste.
We can also get salted and smoked haddock from Eastern Canada. Great for chowder.
When visiting the area, you can find a lot of home curing and smoking for sale, by the roadside, in the Atlantic provinces, as well as Quebec.