Going by the AM rules, I would say no, the AM Emperor/Oberon cannot take the Shark AB option because the rules of the AM supersede that of the Emperor/Oberon. As a race, they do not use ABs, even if that option was available to them via the Emperor normally. Which is why the SM Refits would work because the SM were the one in the ABs.
However, I can also see the Emperor's rule as being the exception to the race rule and being legal. But the race rule overriding a specific ship option is a more stronger case for me than vice versa. In this case, Ray would be the better judge to settle the matter definitively. In that regard, I think Ray would say yes to allowing it in the instance of the Emperor/Oberon.