Well, for one Union in particular, the AWU in the NT, they were under heavy surveillance, due to the Communist influence in the Union... There's a brilliant PhD thesis on the Union, that has a whole chapter on what happened during WWII in the AWU in the NT, it starts at page 181 here:
http://espace.cdu.edu.au/eserv/cdu:6353/Thesis_CDU_6353_Brian_B.pdf