In the game I just finished (China, Regular map, Regent), I used the ROP in a more straightforward way. I was on a continent with Zulu and India. France and Greece each had their own continents, and some others were already destroyed. I was in third behind India and Greece, and had signed an MPP with Greece, France, and India, and started building up my military (early modern age).
I was dead center between Zulu and India, when I attacked Zulu. Zulu and I had equal military, and India was a bit stronger than both of us. When at war, we were all gracious in our unity to destroy Zulu (great for trading, even though France and Greece barely got their boats over before the war was finished). I gave India ROP, so they could send dozens of war elephants across my railroads to weaken the Zulu. Then, I just took over the cities that they had weakened. I took all of the Zulu cities except one I razed (population 25, too much hassle), and one that India took.
The final result was that I had 3/4 the continent, had continued to grow culture, production, and cash through the war, and afterwards I just kept the MPP's with everyone to maintain peace with the world while I went ahead of everyone. Without the ROP, I would've been in a long war, had much weariness, lost production, etc... At the start of the war I was in third, shortly after I was ahead. I built the UN to control the vote, and (barely) won with the Space victory, when I was definitely going to lose otherwise...
So, the ROP helped without any sneak attacks. I've never used it before, as I don't even trade my maps because I like to keep everything real secret and I definitely don't want anyone poking around my cities. This may not work on the higher levels, I just get crushed on them so I still play only the first three levels.