It's a little more complicated than that. Greek banks only have about €23bn in lending to the Greek government, and €30bn to 40bn in deferred tax assets.

However, Greece has not defaulted on any of its loans yet so if the ECB pulls the plug this week it will have to be on the basis of failure to successfully complete the 2nd "programme", not on a loan default. I'm pretty sure the Greek government will find the €2bn it needs to pay the IMF on June 30 so as to avoid being accused of any funny stuff before the referendum.

I just blogged the following elsewhere: Varoufakis on ESM bank recapitalization

It's looking likely that the ECB Governing Council may withdraw emergency liquidity assistance (ELA) from the Greek banks as early as Wednesday (the current "second programme" expires at the end of Tuesday), if not earlier (though I think it could also freeze ELA now and withdraw it on Wednesday). At that point, the Single Supervisory Mechanism could declare the four major Greek banks insolvent and set into motion the procedures foreseen by the Bank Recovery and Resolution Directive. Given the insolvency of the Greek state, "recovery" would involve ESM recapitalisation as outlined in the FAQ above. But, as Varoufakis hints, the creditors would attempt to impose policy conditionality on the Greek state, at which point the Greek government would refuse recapitalisation. This would leave resolution (i.e., liquidation) as the only solution for the Greek banks. And it is quite likely that resolution would involve a bail-in of Greek depositors as Greek banks have very little by way of long-term funding other than time deposits. If the ECB withdraws emergency liquidity from the Greek banks on Wednesday, a decision to wind down the Greek banks could be taken as early as Friday, two days before the referendum.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman