My understanding and experience has been that "fusion" restaurants combined two or more different ethnic foods together. Our favorite local Asian restaurant is a chinese-thai fusion. Their dishes are distinctly one or the other, and some are a combination of the two cultures. Some dishes are actually westernized versions, sometimes with the culinary presentation jazzed up.
I will assume Y&Y being "asian fusion" means there will be food representing several different Asian countries.....Chinese, Japanese, Indian, Thai........and probably some dishes that are a combination.
Tusker is located in Africa section, so it's buffet will be serving African influenced food. The menu is on another thread already.