Personally I enjoy being able to read many of the international news posts and thank the two regular media monitors for taking the time to bring those items to our attention. I certainly don't consider these to be spam posts.
The site may be "Railpage Australia" (and New Zealand) but many of us are either overseas or interested in overseas matters - some are in both camps. I wouldn't wish to lose that content.
Whether or not it could be more usefully managed in another area I'll leave to popular opinion. It is as much News as is the latest press release from Sydney or Perth. Many items are not replied to (but do seem to be read by a decent number of people) but a few initiate healthy debate.
I don't have any problem with "wading" through the pages of new posts to find something of more local interest. I prefer to think of it as "reading" through; I could argue that it takes as long to locate something of interest from Victoria but along the way I might miss fascinating snippets of news from sometimes quite obscure sources.
If one only wishes to read material from a specific area then instead of using the "New Posts" listing why not use the state-specific forums as a first port of call instead?