That's good you were enlightened concerning the greatness of Tulak Hord, perhaps my favorite person in the cyberverse
From my experience being in NSO, I would find it very, very unlikely that they would ever decline to honor a treaty, even if it meant the epic destruction of their infrastructure. There's a reason why they're so close to STA.
That being said, treaties have cancellation clauses for a reason. Sparta cut ties with tC/NPO and had the cancellation time period elapse well before the war began. Therefore, I can find no dishonor in Sparta's actions.