Goldfrapp did an interview with Entertainment Weekly recently. They spoke about the track they did with Christina. Here is an excerpt:

As for their previously reported work with Christina Aguilera, they say they joined her in the studio about a year ago to collaborate on a song that may or may not be released on Aguilera’s upcoming Bionic. “We didn’t finish it, so who knows what will happen,” Goldfrapp says. Adds Gregory: “It was very nice to be asked, very nice to work with her…And then we haven’t heard where it is, so we’re sort of curious to know.” (A rep for Aguilera’s label was unable to confirm whether the song will make Bionic’s final track listing.)

Source: Entertainment Weekly’s Music Mix