MBS and Treasuries ended the day near their best closing levels since the beginning of the month.  It wasn't a given from the outset though, and far from a straight line. 

The first roadblock came in the form of almost comical newswires from a Greek "official."  The wires indicated that Greece's creditors were close to a draft accord that would include a long term solution on Greece's debt.  They were already painfully toothless and generic before the funny stuff started coming out, but the funny stuff completed the picture.  To paraphrase the wires, a Greek debt deal would already be done if it weren't for the mean old IMF.  EU officials later denied that any such draft existed. 

No one knows who's telling the truth and no one cares.  It's obviously not the grand bargain that Greece would like and we're obviously not going to hear that Greece will magically be solvent.  So whatever news may come, it will always be somewhere in between.  Nonetheless, markets gave it some credence (read: US and German bond market weakness), but backed down from those trades when the EU denied the rumors.

Treasuries stayed relatively more elevated with the 5yr auction yet to come (2nd roadblock).  The results were decent, at the very least, and bonds breathed a sigh of relief.  Only 7yr Notes remain on the auction block for May (unless you count the 2yr floating rate notes, but those don't really have a bearing on MBS).