The "Premiere XML" format is actually the FCP7 XML standard. Adobe adopted it. Unfortunately Apple completely changed it for FCP X; the FCP X and FCP 7 XMLs are as different as FCP X and 7 itself. There is a translator tool, though. "X to 7" from intelligent assistant.
So: Media 100 can read Premiere XMLs (as long as they don´t include non-FCP7 compatible extras), but not FCP X XMLs