I'm a Licensed Engineer and been involved with this scenario twice in my career.
First one was B744 dragged an engine landing in EWR and managed to severely crimp the main oil feed pipe at the base of the engine as the drain mast was pushed up and back into the oil feed pipe on impact. It flew back on a ferry flight to AMS for an engine change.
Second one an A346 which had a high oil consumption. At the time Trent 500 were in short supply so that flew to SIN as one had just come of the overhaul facility there.
Both times we had specially trained company crew flown out to do the ferry flight. I remember they said they start the take off role off the runway centre line to give some allowance for asymmetric thrust.
The prep work for dispatch is quite extensive involving boroscoping the other 3 engines, engine fault history check and various inspections. Both preps took 3-4 days and carried out away from main base. For the B744 there was also structural inspections of the engine, mounts and pylon. I think we strapped the fan on the B744 as well so as not to seize it up due to lack of oil flow. The A346 we didn't as the ferry flight was just within the windmilling time limit set by RR.
Most interesting part was as I was the one signing off the Airbus and releasing the aircraft as there is no MEL for inop engine. Quick call to the QA manager who advised that the 3 engine take off capability is part of the TC process and the aircraft is certified for this procedure so just raise a DD for "No1 engine inop - not to be used"!
I think there also a three engine ferry out of SYD with an A380 a few years ago as well by one the ME carriers?