"What I think is more likely to happen (given how strong the support for the Euro is internally) is they are running the presses legitimately to cover the sharp increase in cash circulation due to the deposit run. The one thing they cannot afford now IMO is banking system collapse.
Stepping into the phantasmagorical now>
Next step would be, since the machines are running, they print (covertly this time, with western codes/serial numbers) a bunch of EUR 500 notes on behalf of the government (or government entities) which deposits them in the banks. Deposits appear and the banks are safe.
They like what they see, so they decide to cover more expenses with euro cash. Two venues that I see are retirees and military. Once or twice per year, there is actual cash disbursed without accounting recognition so the budget looks better or within the agreed upon "cuts". There are 2.1 mm ppl over 65, at avg pension 1000 euros, that's 4.2 mm EUR500 notes, or at 100x per stack, that's 42,000 stacks. That's a ~35x35x35 stack "cube", not difficult to produce or manage. Greece is also very concentrated: half the ppl live around Athens and Thessaloniki.
Then there are 108k military personnel. Easy to disburse cash too at say 2000/mo avg once or twice a year.
Also, guessing, there might be a few of the large oligarch suppliers (ie gasoline for all state/military vehicles) that will take cash in full or in part. Or do a three-way deal with a Bulgarian oligarch or two who will take euro cash. The Greek banks have extensive operations in Bulgaria so the money can get deposited there.
So Greece can print legit currency and make its budget look better and better.
The EU has a problem then: is that legit currency or not legit? It will be hard for them to declare vast parts of the currency in circulation (printed in Greece) to be not legit so the only thing they can do is ban printing and take over the machines (could happen). While this is happening, the Greeks start spending fast; typical pre-inflationary crack-up boom, because they don't know what will happen and chances are, most hold Greece-printed currency (no neighboring countries use the euro so guessing low intermix of cash)."