Scott T transformer 12470-2phase to 4803phase

Interesting question. Is the transformer 25 kVA?

Apart from clarifying the kVA rating, can we assume that the transformer is supplied from a 2 phase supply and transformering to 3 phase?

yes the input is 2 phase and 3 phase out put I was told that they can't be loaded more than 60%

You need to know the KVA, the Voltage and Amperage of the pre and sec of the trafo. 2phase or 3phase does not matter for the fuse size. Most important, you have to use a fuse size according to the rating of the trafo. Fusing the secondary part of the trafo is also important.

the trans is 2 -25k pole mounted cans wired to put out 3 phase 480 high leg with 12470 2 phase input