While in Newcastle, New South Wales some months ago, just south of Adamstown Station on the Belmont line, these telegraph poles are still in situ so as I had the camera with me a few photos had to be taken for future reference. The poles are just lengths of rail with timber cross arms. I believe mainline posts are of 80lb rail and 30′ in height and branch line posts use the same rail and are 22′ in height, note the different insulators used. There is a publication on this subject called Line Route Maintenance and Construction if you are lucky enough to have one. Another line that has this type of telegraph pole is Oberon.
I am afraid that I have asked more questions than I have answers on this subject so quite a bit of research by whoever wants to add this type of telegraph post to their layout needs to be done, if any comes my way I’ll put it on the site. There is a comment by Phil White with a link for more information on this subject.