Registration page URL: http://new.mail.yahoo.com/addresses
I successfully registered a new email address with @ymail.com (unfortunately, ilée has already been taken by someone else, wu wu... ...). From the language options on the registration page, it is clear that Chinese is available for Yahoo! U.S., and you can choose between the new domains ymail.com or rocketmail.com or the classic yahoo.com. However, Yahoo! China only offers yahoo.cn and yahoo.com.cn, which means that the new domains are not available in the China region.
The newly registered email address also serves as your Yahoo! ID, just like with Yahoo! China's Unlimited Mail service. When logging into Yahoo! services, you need to input the entire email address as your Yahoo! ID, not just the username portion.