Craigentinny to Aberdeen light locos

[rower40]

There are two loco moves from Craigentinny to Aberdeen (0Z25, 0Z27) each day, and two back again (0Z26, 0Z28). Can anyone tell me what these are for?
(Apologies if this is in the wrong place.)

 

[Darandio]

I believe they are paths related to the Caledonian Sleeper and don't run all the time. They are probably to allow loco moves between depots, I would have thought they would be typically Class 73 when they run.

 

[Whistler40145]

I believe they are paths related to the Caledonian Sleeper and don't run all the time. They are probably to allow loco moves between depots, I would have thought they would be typically Class 73 when they run.

Presumably, the light engine movements are for when the 73s require Exams and if necessary for fixing faults that can't be resolved in Aberdeen