ed_mines wrote:

I know that box cars could be loaded to any destination rather than be
returned to the home road during the box car shortage from the
beginning of WWII to 1947 or '48.

Did this include Canadian box cars?

Were any box cars exempt from this rule?

Ed,

The rule to reload and route foreign car empties was never waived; instead, it was not enforced not only during the 1940's, but also in the 1950's. Thus, the rule could be ignored with impunity.

The AAR's Car Service Bureau could issue a special "BC" orders requiring a specific Railroad to deliver "X" number of empty boxcars to another road at a specific interchange. In March 1947, the B&M was fined for not complying with a "BC" order for not delivering enough NYC boxcars at Rotterdam Jct. NY and to the CP at Wells River VT.

The rule about Canadian cars was not an AAR one, but could be enforced by US customs. If a Canadian car was reloaded and routed via an all-American route, US Customs could deem that customs duty had to be paid on the Canadian car. Canadian customs could extract the same for an American car having all-Canadian routing.

Tim Gilbert