If you have the stomach for it:
Right click on iMovie in the Applications folder and Show Package Contents.
Double click on Contents to open it.
Double click on the Resources folder.
Find: iMovie Theme Music — right click on it and find and select the option to Copy "iMovie Theme Music".
Close iMovie package folder.
Find a disk location you want to save the music then go to the Edit Menu and Paste Item (or type command-V).
Then you can import the individual files into Final Cut.
What I like to do is create an Event for music resources I import. Right click on the (music) Event and select New Keyword Collection. In this case, I just used "iMovie Theme Music", then all I do is drag the folder containing all the theme music files and drop it on the keyword collection label. All the music is added to the music resources event and isolated by the keyword collection when it is selected. (It's much easier than individually importing each file and then trying to organize them.)