Hi Colin
Well I certainly must say thank you for the informative response. Your search of resources for pics definitely adds to the conversation.
I can add a little after searching through some old CDs of mine. No luck finding a provincial plate on a tank either.
I added a few pics below.
Pre-WW2, a tankette in London with a "C" suffix plate and the two Experimental Armoured Cars in Petawawa, each with a "C" suffix plate. The Radio truck is also similarly plated.
The trucks are in St John PQ pre-WW2 and one has an "F" suffix plate while the RCASC marked truck's plate is un-readable. It could have come from the other Sqn of the RCD, that was in Toronto at that time, for some concentration of Regt'l vehicles.
Finally, post-WW2, is a Deuce unloading from an RCAF C-119 in Gander, Nfld, Ex and date unkn. "GS" or "DS" prefix. The the other seems to be a Newfoundland plate. Unsure.
These do support your observations above.
As for tanks in NB after Camp Gagetown opened in 1956 and Camp Utopia closed in 1958, and the Armour School came in 1970, it wouldn't be a lot, but not just a few either. Militia Shermans and a Regiment(-) in Gagetown. 8th Canadian Hussars (Militia) records indicate that in 1952 there were x4 Shermans at Utopia and x5 at Camp Sussex. In 1957, the Regular Regiment of the 8CH was created in Camp Gagetown with Centurions , stayed until late 1959 and were replaced by the RCD.
I had also considered the possibility that the "Tank" plate was civilian, in relation to such vehicles as you mentioned, as well. I cannot confirm that either though. Some plate collectors I've spoken to at flea market etc venues thought it was a Commercial plate for civil vehicle types you mention but not all. Some of the others tended to not be aware of that type on an NB plate at all. As you found, there isn't much of a detailed history in NB vehicle plates use.
My example does look like it has been bolted onto to something at least once.
I'm hoping to meet up next week with a fellow who has a couple similar to mine. He was a black hat hereabouts back in the day too so maybe he can enlighten me a bit more.
Again, thanks for your efforts and the really applicable points you raise. Well done. I will keep looking at photo resources where I can and see what else I can come up with.
regards
Darrell