Good news, i have not used it yet, but this is a good sign that 464xlat is
in Windows Phone 8.1
https://dev.windowsphone.com/en-US/OEM/docs/Customization/Additional_Internet_APN_settings
Android has had 464xlat since 4.3, and it has been deployed as a default
setting to 11 million phones at T-mobile US as well as default to many
phones at Orange PL (8%) and Telenor
Apple: Your move.
CB
in Windows Phone 8.1
https://dev.windowsphone.com/en-US/OEM/docs/Customization/Additional_Internet_APN_settings
Android has had 464xlat since 4.3, and it has been deployed as a default
setting to 11 million phones at T-mobile US as well as default to many
phones at Orange PL (8%) and Telenor
Apple: Your move.
CB