There are some options when AOG and away from Main Base. V-Pod an engine, frieghter an engine, truck an engine or pool an engine.
I have seen RR V-Pod on 744/747, not sure with CF6/PW options for 744. I am pretty sure a twin cannot carry a pod.
Some CF6 models can be transported in modules and shipped in the forward cargo of a 767 with the large forward cargo door option, but it takes a long time to get the engine back together and the AOG aircraft back on line.
I guess it gets down to how quick the airline wants the AOG back on line and how much money it will cost over lost revenue.
Nowdays, speed is not the priority.....!