If you already have a 480 - 208/120 transformer you plan on back feeding you should talk to the manufacturer and see if they have documentation that says that is OK.
Buck Boosts are usually labeled 240/120 - 24/12 but have documentation that shows their use for other voltages.
If you do back feed a 480-208/120 transformer you will not tie in XO, leave it open.
I have done this for temp 480 power before.
