This is a supplemental to the existing FY2007 DoD budget that runs from Oct 2006 through Sep 2007. So the poison pill would force Bush to Veto, the result would be an immediate loss of funding since the last supplemental runs out in April. The Sec Def could rob all other DoD accounts for funding but he can't go outside his agency unless the Congress authorizes it, some funds that are unobligated could be transferred but most funds are colored for certain activities and it is illegal to redirect them w/o congress's Ok.
As for fillibuster, the gambit is that this would force some compromise for a timetable because a fillibuster is a win for the Dems if it lasts past April, no supplemental no OIF/OEF funding equals immediate withdrawal.
this is what happens when you fight a war on the cheap....if the OEF/OIF costs were all inside the DoD budget when it is marked up in the Congress in September of last year then this would have been voted on by the last Congress not the Dem controlled one.
The RATS and some REPUBS would not let this happen. They wanted the war budget in the supplemental so they could keep the actual budget from exceeding the screwball caps that they always violate. The caps are a product of both sides.