Overground using trains in greater anglia colours

[Bucephalus]

Forgive me if this has already been covered, I did look. When I took the London Overground from Southbury station at 6.18 three evenings in a row I was presented with what looked like a class 315 in greater anglia livery. The inside of the train was in poor condition. Does anyone know if these are going to be refurbished into bona fide overground or are they just there due to a shortage of rolling stock? I told my colleagues it was the latter due to the electrification of goblin but that was just a guess!

 

[Cypher]

I remember a similar situation myself not to long ago where a GA class 317 8 car pulled up at turkey street in the evening peak and reverted to GA Hertford East services once it got to Liverpool street, if I'm not wrong there are a few services run as London Overground with GA stock, I think due to some sort of pathing reason or perhaps helping out London Overground, perhaps someone else could expand?

 

[87015]

Two morning and one evening peak trips are booked to be operated by GA 317s as part of how the workings were split when devolved, which should end in December (new stock on both sides dependent)