So how do/did the Ecudoran/ 1990s Argentinian adoption of the US Dollar work then? Is there a formal arrangement of kinds between their central banks and the Federal Reserve?
Bosnien/Hercegovina uses Euro as a legal tender without being a part of Eurozone. I am not sure whether it is a result of official agreements with the ECB or just their decision.
I don´t think that an independent Quebec would under no circumstances become a part of the Eurozone. But I assume that first they would want/have to become an EU member, and this would have to have been approved by USA - since the rest of North America is clearly their (inofficial) zone of influence. It would be interesting what horse trade would be required to gain their agreement. OTOH in such a situation Quebec may be seen as a possible US puppet / influence channel / lobbying gateway in the EU (a là Poland under the twins but easier to control).
It used to have the D-Mark (to which it was pegged before teh Euro introduction) as legal tender, though. Same with Montenegro and Kosovo (both even before independance). We used to have a neat little currency colony on the Balkans before we introduced the EuroBosnia doesn't use the euro. It uses it's own currency, the convertible mark, which is pegged to the euro.
Actually, it'd probably be "dollar". It would be amusing if it were officially called 'pièce'.In order of plausibility the currency used by an independent Quebec would be:
1. It's own currency (probably a "franc")