If Austria or Italy had referendums that decided to leave the EU they would do so (And leave the Euro at the same time, obviously). Whether or not it's technically o legally possible to leave doesn't really matter.

I don't consider it likely but I also don't consider the current political climate "rational", sadly.

The Eurozone is really what should be dismantled, because it's flawed by design. I'd hate to see the union itself which is originally a peace and trade project disintegrate because of a flawed currency and disagreements on people movement.

The point is not if another country like Austria or Italy would/want to have a referendum. If a country just dislikes the EU and wants to leave then the outcome of the UK/EU deal will not make a difference.

What matters though is if another country thinks they can leave the EU with the outlook of a "better" deal outside the EU. The EU would fall apart if countries would believe that, but what I tried to say is that the EU doesn't really have to fear that, because no other country is even remotely in the same position as the UK, so the chances of a "better" deal outside the EU are almost non-existent, because the fact alone that they don't have their own currency would makes significantly more difficult.

Therefore the EU can actually work out a good deal for the UK and the EU without jeopardizing the EU membership of others. Makes sense?

I think the driving force for a leave vote anywhere, just like in the UK would be immigration mostly (ironically perhaps mostly non EU immigration fear, which is hardly a EU matter) and pure populism in the form of "we don't want to be governed from Brussels". The question is just if the fear of the (economic) consequences outweigh it. I fear that voters of several EU countries would accept severe economic consequences, or at least the risk thereof, because immigration or because Brussels.

Italy won't vote out because of a "better deal outside" (nor do I believe the UK did!). They'll vote out if populists can convince them there will be fewer immigrants without disastrous economic consequences.

In Italy referenda on international treaties are prohibited by the constitution.

The only option is an ad-hoc constitutional law that allows for a specific (non-binding) referendum and requires a large (2/3) majority on the parliament. Interestingly, this was last done in '89, to vote to transition from the (economical) European Community to the (political) European Union.