So Serebii is updating the Trainer list for the PWT. Bianca is a battleable person in the PWT in the Driftveil Tournament, Mix Tournament, and Unova Leaders. She's also in the World Leaders tournament, although Serebii listed her twice with the same team.
Why is she in the Unova Leaders and World Leaders? XD
So far the only Pokemon restrictions I found are:
The following aren't eligible; Mewtwo, Mew, Lugia, Ho-Oh, Celebi, Kyogre, Groudon, Rayquaza, Jirachi, Deoxys, Manaphy, Darkrai, Shaymin, Arceus, Victini, Reshiram, Zekrom, Kyurem, Keldeo, Meloetta