I think it's premature to compare China's assurances that it will buy Greek government-issued bonds when they return to the market to the Marshall Plan, as Véronique Salz-Lozac'h does. But I agree that the Chinese commitment to Greece is very significant, for two reasons.
First, it represents a bridgehead for China to develop closer bilateral ties on a win-win basis with EU member states. Given the tenor of EU-China relations at the moment, as well as the size advantage that China sacrifices when dealing with the bloc as a whole, that works to China's benefit. Keep in mind, too, that the issues currently driving EU-China tensions -- appreciating the yuan and loosening Chinese import controls for EU goods -- are essentially German and French issues. In fact, Greece would benefit from being able to adopt China's policies vis à vis Germany, as well. So this is a net win for China and raises the possibility of another potential faultline for the EU, similar to the kinds of bilateral approaches the U.S. uses when reaching an EU-wide agreement is too constraining.
Second, it highlights the relative weight of China and the EU as actors in the global financial arena. This kind of guarantee from China will have a significantly calming effect on market fears over Greece and its debt. In fact, the Greek debt crisis was fueled at one point by reports that China had refused to buy up an offering of Greek government-issued bonds at under market interest rates, which at the time were particularly onerous for Athens. Compare and contrast that to the EU's efforts to calm those same fears and you'll see what I'm driving at. The EU did ultimately manage to backstop Greece, but it came at significant political and economic cost. And even now, it's not entirely certain that the instrument the EU finally arrived at will prove to be effective if needed. Beijing, on the other hand, can achieve the same results with a stop-over visit on the way to an acrimonius Asia-EU summit in Brussels. It's particularly ironic that this demonstration came at the very time that China and other Asian nations were demanding that Europe relinquish some of its disproportionate voting shares at the IMF to give emerging economies more say in the fund's governance.