BT.com, a major UK portal, was powered by Yahoo Search, but is now being powered by Google Search. Why is this a big deal? Well, the portal is a partnership of some sort between Yahoo and BT, i.e. it is hosted at bt.yahoo.com.
Now we all know that Yahoo and Microsoft have made a big deal, where Microsoft will hopefully take control of all of Yahoo's search technology and power that side of their business.
So why did Yahoo partner up with Google on this portal and not Microsoft Bing?
Eventually, Yahoo said all their properties will be "powered by Bing Search."
A WebmasterWorld thread said that BT members just received emails from BT saying:
Your BT Yahoo! Search is now powered by Google, the UK’s most popular search engine.
This shouldn't confuse anyone down the road.
Forum discussion at WebmasterWorld.