Batb can be cloned unless japan paid for exclusivity for a certain amount of years. But I am guessing if they did then this entire thread wouldn't be a discussion and given Magic Feathers comments on "clone wars" this would indeed appear to be just that. A clone.
One thing I am confident about... if BatB could be cloned and MK build the same ride in the relatively near future (open by 2021) then Tokyo would rightly demand for Disney to cover their share of the R&D costs. This would thus ignore the entire cost saving "value" of using a cloned attraction.
Meanwhile, Ratatouille is already build and paid for. Cloning that would not require additional R&D costs. So, I think that is a point in the Rat's favor in terms of what could be chosen and is quite possible why it might be "in the lead" per insiders. Also, the ride might just be generally cheaper to build.