Online about about a month ago, officially online today, Yahoo News has added a link on every search news search results page (right column) that allows the searcher to add the search query directly to their My Yahoo page. New results will be delivered as a "feed" on My Yahoo pages.
It's possible to create and transport advanced queries to a My Yahoo page. However, you cannot limit to a specific source.
As of today, RSS-based delivered Yahoo News search results will only work with My Yahoo.
However, later this week, look for a second button on the right side of the page which will allow you to take Yahoo News search result feeds and add them to ANY aggregator.