While Apple does not provide a direct inclusion of FCPX/iMovie sound effects library in LPX, you can get them to load and be available in LPX loops library.
In Finder navigate Macintosh HD>Library>Audio>Apple Loops>Apple>Final Cut Pro Sound Effects.
Right click and create an Alias.
Install the Alias in Macintosh HD>Library>Application Support>Logic
Launch Logic, Open the Loops Library (the Loops icon upper right) click on the "List" icon; select "All" and your sound sample will appear there using the name of the FCPX sound sample.