Multiple UV Shells?

Hi all, I am attempting to run a Mari/Maya based workflow through to UE4, and the models have multiple uv shells, each with a different texture map attached.

I read everywhere that UE doesn’t support this, but the models import okay, and create the material nodes per shell.

What is happening here? Are the shells being moved back to 0 - 1 space? IS there any support for multi-shell uvs?