I found this 2004 piece (pdf) by Shmuel Bar. It has numerous interesting and detailed points, though I do not think it can be considered objective. Here is one excerpt:
Iranian negotiators are methodical and have demonstrated a high level of preparations and a detailed and legalistic attitude. On the other hand, their communication tends to be extremely high-context; ambiguous, allusive and indirect not only in the choice of words utilized, but in the dependence of the interpretation of the message on the context in which it is transmitted: non-verbal clues, staging and setting of the act of communication, and the choice of the bearer of the message. Procrastination is another key characteristic of Iranian negotiation techniques. This stands in sharp contrast to American style communication (Get to the point/Where’s the beef?/ time is money!) which places a high value on using lowest common denominator language in order to ensure maximum and effective mutual understanding of the respective intents of both sides. This tendency has been explained by an aversion to an assumption that the longer the negotiations last, the greater a chance that things can change in his favor and an intrinsic Shiite belief in the virtue of patience.
Dissimulation, high-level disinformation and manipulation are widely acceptable.
…one may paraphrase Marshall McLuhan in saying that in Iran frequently “the messenger is the message.”
…One of the characteristic traits of Iranian negotiation techniques is that the haggling goes on even after an agreement is struck.
I suppose we’ll see how it goes.