The narrow gauge was cable operated so this would probably have also been electrically powered. In the claypits themselves it was quite possible for the draglines used for extracting the clay to be electrically powered also, it would be far easier to lay a cable than to deliver coal or oil to the pit. The kilns would have been coal fired, as evidenced by the tall chimneys that once abounded in the area. IIRC the waste heat from the kilns in some brickworks was used to generate electricity.