I thought I'd add a little additional information from sources I have on hand to this discussion:
In 1953, the Dominion Bureau of Statistics reported 2,875,483 tons of Anthracite coal received from foreign connections (i.e.. the USof A). That represents 70% of Canadian Anthracite traffic. The overwhelming majority of that traffic, 1,582,640 tons, came into Canada delivered to the CNR. Next closest was the Canada Southern (NYC) who received 537,751, or about 13%. A line I know nothing of - the St. Lawrence and Adirondack was third, receive 256,919 tons, followed by the Napierville Junction, that received 232,968. The C&O Pere Marquette received 131,408 tons. Not sure what conclusions may be drawn from these figures, besides the obvious one - the anthracite was coming to the Canadian Industrial centres in Ontario and Quebec. In contrast, the CPR received only 45,063 tons.

Virtually no Bituminous or Lignite coal was received in Canada by any line from the USA.

According to the annual December Summary of Monthly Traffic Reports for 1953, (which give different annual totals - so another system of counting was used - (e.g.. total anthracite received from "foreign connections" was 2,644,981 tons)) 237,932 tons of Anthracite received from the USA was delivered back to the USA. All told, freight delivered to foreign connections lists 288,531 tons of Anthracite delivered to the USA. That's an odd figure, as Canada only originated 27,567 tons - so I'm not sure where the remaining 23,032 tons came from. Perhaps some ship-born movements?

The then relatively new Province of Newfoundland did no trade in Anthracite in 1953. Tiny Prince Edward Island loaded 56 tons, and unloaded 3,702 tons, but received none of it from the United States. Nova Scotia loaded 461 tons, received 5626 tons from the USA destined to points in Canada, and unloaded 14,196 tons.

The Province of New Brunswick must have been a flow-through point for the shipment of Anthracite. Only 145 tons were loaded in the province. 21,472 tons (about 20,000 tons of which was received from Canadian connections) was unloaded there. Only 152 tons were received from foreign connections and destined to foreign connections. But 3,546 tons were delivered to foreign connections.

Quebec loaded 6,996 tons, received from the USA 859,220 tons destined to Canadian points (622,346 tons unloaded in Quebec), and delivered 10,405 tons to the USA.

Ontario dominated the Canadian Anthracite trade. it loaded only 19,749 tons, and received 2,021,541 tons from the USA. 2,022,345 tons were unloaded in Ontario, and only a trivial 274,490 tons were delivered to USA connections.

Manitoba received 110 tons of Anthracite from the USA, and sent none south.

Saskatchewan unloaded 55 tons without loading any and receiving none from the USA (directly).

Alberta unloaded 118 tons without loading any in Alberta and receiving none from the USA (directly).

British Columbia unloaded 64 tons, loaded none, received none from the USA, and delivered 30 tons to the USA. Is that 3 cars?

As for lower grades of coal, only 346,690 tons were shipped south out of Canada to the USA. Meanwhile, approximately 4,380,000 tons of US lesser grade coal was sent north. As others have already said, the trade in across the boarder was almost entirely north bound. The trade south was trivial to non-existent.

Rob Kirkham