Can APK expansion files be moved to the SD card without root on the Moto G (Android 5.0)? It seems as if Motorola has reimplemented the ability to move apps to the external SD card on their recent devices.

Does this only apply to an app's .apk file, or will Motorola's implementation also move the (usually much larger) APK expansion files a.k.a. OBBs to the SD card when moving an app?

I understand that the app's data and cache files will not be moved unless the developer specifically implements SD card support.
.OBB files are usually large and they will be/can be moved to SD card along with app data. Sometimes only .OBB files will be placed on SD card and app data is kept in internal memory for faster startup.