The records of personnel who enlisted but only served within Australia, usually as depot troops or camp guards, are contained within the series of records MT1486/1. To search for individuals in this group (series) of records I recommend that you click on the 'RecordSearch - Advanced search' tab, click on the 'Items' box and then enter the name of the service personnel into the keywords field and MT1486/1 into the series field then click search. Unfortunately, not many of the items in this series have been digitised, so you will need to purchase a copy of the record - for information on how to purchase digital copies, please see http://forum.naa.gov.au/forum/topics/purchasing-digital-copies-onli Our WWI service records for service personnel have all been digitised, and you may be able to find the soldiers you are looking for if they saw active service overseas in addition to their domestic service.
Please note, I am not sure whether all of the records in series MT1486/1 have been entered onto RecordSearch, but there are more than 20000 items listed.
Also, when I had a quick look for records we might hold on camp guards, I noticed a number of personnel who served as concentration camp guards were court martialled - you may find additional information about the soldiers you are interested in if you have a look for court martials as well - these are held in the series A471 (search as above, but in place of entering MT1486/1, enter A471).
Best of luck with your research