Queen's Brian May have mentioned that he has discussed Lady GaGa singing with them. Here's an excerpt...
"Gaga, whose stage name was inspired by Queen's 1984 hit 'Radio Ga Ga,' has been in talks with Queen guitarist Brian May about the collaboration, as May told Britain's Daily Express. "We talk about going out on the road all the time but there's a bit of a singer problem to put it mildly. We get a lot of offers to work with other people. I worked with Lady Gaga and she's very creative and is someone we've talked about singing, fronting the band with."