The main target of Greece's austerity plan, before even the European nations being expected to offer bailouts, was the bond market. Greece needs to at least partially finance its way through the mess it's created, and with markets worried about a fairly imminent collapse, that was proving difficult.
But the negotiations with the rest of the eurozone, and the recently released austerity plan, seem to have given markets the needed reassurance. Greece closed a ten year bond issue today, raising about $20 billion at a 300 basis point premium. That's pretty good for a country that recently seemed to be on the brink of some sort of major financial crisis.
On the other hand, whether the plan is "working" kind of depends on your perspective: civil servants just blockaded the finance ministry.
Update: Ack! The offering got bids of $20 billion, but raised less than that. Mea culpa.