Yahoo! says that "they've started testing organic (algorithmic) and paid search listings from Microsoft for up to 25% of Yahoo! Search traffic in US." "The primary change is that listings are from Microsoft, overall search page should look same as earlier. Those into tests, might notice how select search results displays due to variety of product configurations testing. In this picture, "boxed areas of search results page are from Microsoft's platform, while rest is powered by Yahoo!."
In coming months, Microsoft's mobile organic and paid search listings will be integrated into Yahoo! Mobile search, for fans in US and Canada to see Microsoft organic and paid search listings on their phones.
"we anticipate that US and Canada organic search listings in both desktop and mobile experiences will be fully powered by Microsoft platform beginning in August/September timeframe, and paid search in October," stated Yahoo!.