While I think it is likely that this story is the typical overblown story about military contingency planning, it is definitely something worth looking at. The US military has plans prepared for all kinds of possible required military actions. The fact that they have plans to attack Iran with nuclear weapons is not suprising in the least. It does, however, focus attention on the situation in Iran and what there is to be done about it.
UPDATE 4/09/06 10.02PM: My suspicions on the non-earthshaking news that we have military plans to deal with Iran are supported by this story.