I received some line pole information from Ian Millard and Colin Hussey in the comments from my last post and then received an email from Bob Stack of South Coast Rail with some very interesting documents.
Bob's documents were two NSWGR documents and a plan which I have uploaded to Google Docs for you to download.
Document 1 - SRA NSW Line Route Maintenance and Construction Q&A
Document 2 - NSWGR Erection and Maintenance of Line Work 19/10/1950
Document 3 - SRA NSW Line Pole Construction Detail Plan 13/04/1984
These cover anything you might want to know but you will have to look for it particularly in document 2.
For instance there are Sag Tables and I have found that the sag in between two poles spaced 40 yards (120') apart at a temperature of 70 degrees F is 6.3" for galvanised wire and 5.7" for copper wire. As my poles are approximately a scale 100' apart then the droop would be about 1.5mm actual. There are tables for spans of 40, 55 and 60 yard but because of our tight curves we need to space the poles a bit closer, I didn't know how far apart they were in reality so I spaced them to look right.
Anyway, a big thank you Bob and everyone, have fun reading if you download them.