The setup could be identical to ST2: the RNZ could be teeming with Klingons, perhaps as the result of the oft-suggested but only vaguely verified alliance between them, perhaps simply because they were marauding. Having Romulans in the RNZ would be automatic cause for war; having Klingons there would be a risk to be assessed, and the Kelvin
had found out that the Klingons were keeping their distance (albeit a minimal one) and Robau could probe further.
Klingons at the very spot of Nero's emergence and a battle with Klingons (somehow involving a Klingon prison planet, although AFAWK only in the relaying of the message) in connection with Spock's emergence is IMHO good support for the idea that the two emergences take place at one and the same location. That's a pretty intuitive and consistent thing to build speculation upon. And ST2 gives us the excuse to say that the presence of Klingons amusingly speaks of the RNZ, the location we want for the exploding star which supposedly was the point of departure for both time travelers. That latter bit's a fancy "out" from a poorly written story, but hey, it works. Sorta.