Microsoft Taiwan has put up a website indicating the availability of update of Windows Phone 7 to Mango firmware. The two phones that are supported are HTC HD7 and Mozart. Although Microsoft Windows Phone 7 supports updating using Zune, the Mango update will not be delivered through this method. Instead, end users have to bring the phones to the locations indicated at this website to do a flash update by person.
This is probably because, the current firmware are European firmware which has no Asian language support (menus and input). So the new firmware will probably erased everything and start off from scratch. The online update probably does not support such a feature to clean up the firmware totally but leave the base language intact. That is why a clean flash is required at the selected service centres.
Below is the link to the Microsoft Taiwan site in Chinese