Even though they're both well known for the left hook i think it probably wouldn't play the main role. I see Oscar being wisely wary of Pipino's key weapon and stick to using his jab and movement. The advantage in height and reach would allow him to avoid most of the serious danger.
One of the things that has always stuck in my mind about the Trinidad v Oscar fight is the first thing that Oscar said in the post fight interview:"I didn't get hurt." I think that he would prepare for Cuevas with the same mentality, and that anybody that entertained the idea of ever planting the feet and throwing a left hook would be run out of the gym. Oscar would move and jab and move some more. He would probably win but there would be several better fights in the audience. This fight would sell out the Forum and the fans might burn down the building and Oscar would have to move up north.
I can see a few possible scenarios for how this fight plays out. -Oscar using his speed and skill to win a safety-first decision is certainly a viable one. -I wouldn't rule out that Oscar takes Cuevas out early if he catches him coming in with some well-timed hooks. At the same time, I wouldn't rule out that Oscar becomes frazzled or fades late under Cuevas strength, power, and pressure.