Sharing content with domain access?
One solution I did recently in a similar situation was just create a views xml feed of the content I want to feed to my subsites. From there my subsites would have the feed_import module and have to fetch the articles every 10 minutes. Once fetched it will be unpublished but can only be viewed by certain roles for screening. 

Now as for the left over imported nodes I would use node_purge to delete nodes that are X days old. Obviously this solution wouldn't be ideal for sites with sensitive data as the xml feed is exposed.