Yeah the whole thing is bi-directional AFAIK (extension). Even on places where a train would NEVER run east-bound down the west-bound, there are coloured lights for it. I guess it would only be used for wrong directional move situations. Would be a whole lot easier for the driver to just change ends and go back under signalled conditions than the whole form procedure. But this isn't trained to the drivers as far as I remember. Oh anyway I mite be wrong about the whole thing... but all the main line shunts are with coloured lights and harbour lights, none are shunt signals. Also as towerman says when trains are leaving SFD platforms into the depot, say a train is leaving P 14 at SFD to the depot, usually the train arriving into SFD would have to wait outside at a red until the train was in the depot reception road. But it can get a green with harbour lights to the right and switch the the WB track going EB into SFD platform 15 whilst a train is leaving platform 14 going to depot
Having once seen the signalling diagram for the JLE, I'm sure that only certain sections of the JLE are bi-directionally signalled, mainly around crossovers, and the depot/terminus areas.