Suggestion: Cables can be moved by pistons

cables cant,as they are now entities.try installing hippoplatimus's patch,it should make it work.

I tested that patch and it won't work. Cables are not entities, they are Tile entities, which is again something different^^ But for a simple switch you can use a transformer:
Cable is wired from below into the 3-dotted side, the transformer outputs 512Eu/s on its sides if not powered, if powered it would emit 2k EU/s, but as the MassFab doesn't send energy into the transformer nothing happens.

If you want to use pistons you could use (I guess) them to move a transformer, but I haven't tested that yet.