The process was developed because wide bodied freighters were not around in enough numbers. They add a fairing to the front fan and to rear of the unit, to reduce drag and to prevent the engine windmilling in the breeze. It's probably very cost effective for a carrier to transport one for themselves, than pay freight charges for one on a metal pallett. Or even pay someone else to ferry it on a schedule rotation to get another 747 operational again more quickly.