Yes, it's pretty old news (at least in the US and Canada): http://arstechnica.com/microsoft/news/2010/08/yahoo-transition-to-bing-finalized-in-us-canada.ars
I think I heard this news before, but I did not believed. Its more of like a partnership of Yahoo and Bing in my opinion.
Last I checked its powered by Microsoft. Not Bing itself. But I could be wrong. I received an email about my ads center of yahoo merging with that of Microsoft
Perhaps its true, I've heard before about their connivance, I don't think Google have to worried about such issue.