Yahoo! Video Search will allow you to search every word spoken during television news broadcasts from the BBC, Sky News, and Bloomberg. You'll be searching the closed captioning associated with the broadcast and then can click to view the full-motion video of your search terms being spoken.
It's worth pointing out that video search databases like BlinxTV and audio search database, Speechbot, use speech recognition technology to create a searchable transcript that you search by entering keywords into the search box. BlinkxTV offers content from many television and radio broadcasters (including the BBC) while Speechbot offers more than 15,000 hours of keyword searchable radio programming.