Well...the question is, how does this happen?
Something along the lines of the Dayton accords isn't going to be supported by either side, and certainly not by the other Arabs, and there's little reason to think that anyone would bother trying to impose it. Especially when all of the groups that had any desire to meddle also wanted Jerusalem as an international city.
Anyway, let's say that somehow we get Bosnia in Palestine. I'd argue that such a set-up can only occur after terrible blood-shed because, frankly, it's an arrangement that everyone hates and only goes with it because it's better than continued genocidal war. So I'm not sure that you can avoid war breaking out, especially given the "provocation" of the flood of Jewish immigration (though I guess you could get some other country to take them, or not kick them out in the first place, but that's basically ASB).
Anyway, whatever, let's say it happens; maybe after a terrible war with no clear winner and for some reason the UN decides to intervene. How does it stay stable? Initially at least, with a large foreign peacekeeping force. With any luck, after a generation or so of living near each other without too much violence, and increasing economic prosperity, the two might come together.
Now, there is one way in which Palestine in the 40s is not Bosnia in the 90s or Belgium ever: the large number of other Arab nations around, most of whom were none too happy about Israel. Even if the local Palestinian Arabs are willing to play ball (a big if, of course), those in Egypt and Syria and Jordan are less inclined to do so, especially since each of those countries has a more-or-less valid claim to the territory and her [Arab] people. And this problem isn't going to go away. Even if, say, the presence of UN peacekeepers to keep Palestinian Jews and Arabs from killing each other also helps keep the other Arab armies out, Arab nationalism is probably going to happen like in OTL, and pan-Arabism, and it's going to sweep up Arabs in Palestine just like anywhere else, and keep up constant, if not increasing, pressure for a unitary Arab nationalist state.