I don't have any evidence that there are subcategories, but as a journalist once said to me, the number of Canadian journalists is small to start with. When you break it down by region and specialty, it gets smaller still. When you see a request come in on some topic pertaining to some region on a specific issue, and you know it's a journalist's request, sometimes it's very easy to figure out who the individual filing the request is.
On October 18th, 2006. See this statement in context.