It's true that we don't know. It's also true that it's different now than it was in 2004. And we know more about what specific activities the Iranians are involved in within Iraq's borders.
It's helpful to watch what's going on in Iran internally. Because it's reasonable that the true intentions or wants of the Iranians may not be stated in these negotiations.
Ahmadinejad has stated openly that he doesn't respect the West and he belittled the "processes" of diplomacy. This doesn't mean that he doesn't know how to use the tools of the West against us. There may be a specific request in these negotiations with an intent to divert attention from the underlying issue.
He's not in good shape at home or in Iraq and these are important notes to keep in mind.
Ahmadinejad is really a figure head. The real power lies with the Assembly of Experts and Supreme Leader Ali Khamenei who replaced Khomeini. There are many things swirling about Iran these days including UN sanctions, nuclear weapons development, and domestic unrest due to a failing economy and corruption. The seizure of the UK sailors may have been for domestic consumption and to placate the powerful Revolutionary Gurad who are unhappy about the detention of their compatriots in Iraq. It is also interesting that since the seizure, the price of oil has gone up bringing in more oil revenue to the Iranian coffers.
Thus, we should be very careful as to how we react.