ECB won't go nuclear if we default on promissory note – look at Greece
THE ECB never does anything without an eye on global trends. In the overall scheme of things, despite the fact that it's the "European" central bank, things that happen in small European countries matter little in setting the tone. In contrast, what happens in big countries, with competing currencies to the euro, matters a lot.
When it comes to small European countries, the ECB's tactics are always the same: threats, nasty leaks, warnings of Armageddon, and orchestrated press releases, all followed by a well-disguised climbdown. Expect the same here.
The reason for this is that the ECB has no conventional weapons but it does have the nuclear option: when a country can't pay its debts, the ECB can cut off the banking system from ECB financing. This brings the country down, which will cause chaos not just for that nation but, via contagion, for the whole euro system. So the ECB is condemned to climb down. The best example is Greece – it's a four-time defaulter within the euro, and yet money still comes out of its ATM machines in Athens.