FCPx doesn't recognize Premiere Pro CS6 XML

FCP uses a different form of XML. You might try seeing if the 7toX application will handle it.

THe only application I'm aware of right now that will allow you to convert a Premiere XML to FCPX is Black Magic Resolve. They have a free version of the software. Resolve is not the easiest program to use, but it's worth learning how to use it just for the utility it can offer.

I'd give 7toX a shot. Resolve is a pretty steep learning curve.