I believe that the empty site in the middle of this picture is the where the generating station for the electric lights in Lambton was located. The generators were situated between Young St (now Newcastle Rd) and High St, in a former quarry. The electric lighting scheme sent the council bankrupt, and the generators were sold off in 1904 and the building housing them demolished. An earlier photo of the generating station from 1890 (below) taken looking north from Young St/Newcastle Rd shows a long thin rectangular building behind it, and I believe this is the same rectangular building that can be seen in the photo above.
A close up from another photo of Lambton from 1900 (below), looking north, shows buildings that match the photo above.