IRSE Australasia was formed in 1947, with the impetus coming from Mr L Martin, the District Engineer for Signals and Telegraphs in Goulburn, NSW. Some of the correspondence relating to the formation has been preserved and is available here. (Please note that this is a very large scanned file).
C.B. Byles was a leading figure in the formation of the IRSE in the UK and continued to be influential when he moved to Australia.