You can import the Schildbach backup file directly into MultiBit, just change the file extension to *.key so it can find it in the file dialog. This is very useful when your phone is stolen, if you have a Multibit installed on your Desktop and ready to use and are familiar with it then you can quickly import the Schildbach backup on your PC and send all funds to a safe address before the thief figures out how to do it. But you should not use the same keys in both applications in parallel, this will cause strange effects (coins magically disappearing in the other wallet), do this only if you want to permanently move all keys from A to B.