After some digging around with the Wordpress XML-RPC documentation, it seems that there isn't a way to remotely obtain a "post" (such as a news article) through the XML-RPC interface. The documentation only mentions wp.getPage - if I try and pass in a PostID to this method, it returns:
[faultCode] => 404 [faultString] => Sorry, no such page.
... but wp.GetPage obviously does work when I pass a valid PageID. Does anyone have any ideas how I might go about solving this? Ideally, without extending the XML-RPC mechanism on the remote site (as access to these could be tricky)