The Diplomatic Corps are representatives responsible for foreign relations to various countries.  The diplomatic embassies for all countries are located in our Nation's Capital, Ottawa.  The Diplomats and their support staff who are not Canadian citizens receive receive distinctive red plates issued in Ontario as all such vehicles must be registered using the address of the embassy in Ottawa. Quebec has issued Diplomatic plates since 1952 for the International Civil Aviation Organization (ICAO), a UN body based in Montreal. 

The diplomats have always had "CD" on their license plates since 1946. Beginning in the mid 60s, support staff received plates with an 'F' prefix to denote "foreign", later this was changed to "ALN" to denote "Alien", and finally "XT" for "External". Examples are shown here.

Based on a treaty with China, Canada, along with many other countries, do not recognize Taiwan as as independent country. For this reason full diplomatic status is not granted, rather we see them as a foreign organization. They receive special red plates like the diplomats, except with the letters "XOR".

Branch offices (consulates) perform similar functions and are located in major cities coast to coast.  Consular Corps plates are issued by most of the provinces which have a consulate. 

Diplomatic Corps Plates before 1959 were normal passenger colors Since 1959 they have been white on red Heads of mission received numbers below 20. First plate issued to a Taiwanese official. Issued to ICAO Personnel

Diplomatic Staff F = Foreign (1963-72) ALN = Alien (1973-74) XTR = External (1975 - )

Consular Corps This looks like another Diplomat plate but it's actually Consular  Corps.

Alan Betts: Man '69 CC
Rest are attributed to the webmaster.