This isn't the first time we've played footsie under the table with Iran.
During the Afghanistan invasion, the US received covert cooperation from the Iranians, but then the Axis of Evil speech came along and everything turned around. No one can say that the Iranians don't look out for number one first, but GWBs sudden turn-around blind-sided them
and they have worked actively against us ever since.
Iran had practical reasons for working with the US at at the time, as a Shia state, it was concerned about the growing Sunni Taliban threat on its eastern border, and it had it's hands full dealing with its troublesome secular neighbor Iraq to the west.