What are you talking about? Did you read the article? Google setup a test explicitly to see if Bing was doing this and got pretty conclusive evidence they were. Now if Google was doing the same thing, why would they call out Bing on it? They'd have a huge risk of having it fly back in their faces if Bing could prove the same thing in reverse. "Watching" is another matter; of course Google and Microsoft watch what each other are doing, but there's a big difference between that and outright copying *results* without actually figuring out algorithmically how to generate the correct (or similar) results.
Even if Bing could prove it in reverse, Google evolves their algorithmn in a much more rapid pace and are much more respected by everyone that it wouldn't hurt them at all plus they could always market this as bringing meta-search engine to the next generation Google style.
Bing on the other hand being the new kid on the block has the problem of needing to prove they are bringing something new to the table. Any other search engine would be "ok" since it's very hard to mimic Google's search quality especially if they are reinventing the wheel but since Bing wants to be a major player, it's advantage Google if they can portray Bing as merely "Google wrapped in Microsoft's interface" since that puts Bing right back down to the other search engines that "tries" to be Google and are not really big fishes. Just pretending to be one.
Although... the morbid curious in me wants to know if anyone would ever bring that old article where some bloggers wrote how Bing image searches get more "porn" search results than Google. Wonder how both company would reply to that.
P.S. My other morbid curious self would want to see DuckDuckGo proclaim they are copying Google search results just so that search engine would get extra PR especially if it will lead to more bloggers explaining why DDGoog's search result are inferior to DDGo as I've read some say.