Yes

The file with the actual songs is here:
~/Library/Containers/com.massimobiolcati.irealbookmac/Data/Library/Application Support/iReal b/UserSongs.plist

and the file with the playlists is here:
~/Library/Containers/com.massimobiolcati.irealbookmac/Data/Library/Preferences/com.massimobiolcati.irealbookmac.plist

Restore those two files.