Found this thing while looking for an explanation : http://www.capercailliebooks.co.uk/wp-content/uploads/2014/09/Linwood-and-the-Hillman_low.pdf . The Spring Special you're talking about is in page 30 . Tried in english and french to have an idea of why we would have ordered a RHD version or why the order was cancelled but found nothing else than the fact that the order was cancelled . Could understand if it was the van and it was set to be used for deliveries as we had for a while before they switched to the Ford Transit Connect ( which, ironically can do the same job while being LHD.. ) but this job is clearly not the Spring Special's purpose.... Newfoundland is the last place to drive on the other side and they did change in 1947 ( according to some websites ) before entering Canada in 1949.

I think it might be a : an error somewhere in the order ( no matter if its an assembly error or an administrative one ) but i don't really believe its the reason, i mean, its a car manufacturer, not a single guy who works in his garage during the weekends...
or b; creating a really special, collectible edition of it and the idea was cancelled either by the manufacturer or the ones who imported the cars in Canada...

Was the regular version of it selling well in Canada ? if not , might be why it got cancelled . Probably was an easier ( and money/time saving ) operation just to switch it from LHD to RHD like you said and sell it as a special edition instead of removing all the CDN-spec stuff from it