I made a test post to try this out, and got the following in the metadata section:

    xpost: http://mumblemutter.livejournal.com/xxxxx.html

This is obviously crazy cool (!!!), but I'd love to have customization options for this eventually. Like the ability to wrap the link in custom HTML or change the "xpost" to something else. Until then I'll probably keep adding the LJ link manually into the post. (Yay OCD!)

Also, cut tag niftiness! So much awesome!