This isn't a standard function in eZ publish, I will recommend you to look at http://ez.no/community/contribs/applications/ez_keywords_nodes, this is a extension that can help you with your keyword export.
Good luck :)
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Well I'm roughly a year too late in this - sorry! But if anyone else comes across this thread then a partial solution is to create a custom content class that uses a custom override template which does a "fetch", based on criteria inputted by an editor (for example) into an instance of the new content class.
I called this custom object a "Smart Folder" (We used to use the Plone CMS and they have this sort of functionality out of the box complete with RSS). See my thread here for how to do this. I'm working on integrating the RSS into it right now, hence my stumbling across this thread.
