In the continuing sitcom that is popular music - and also in real life - Sting and Paul Simon once lived in the same building on the Upper West Side of Manhattan, they recalled in a recent telephone conversation. "For 20 years, this guy would be borrowing things all the time," Sting said, in a tone of mocking complaint. "Then I heard he was a songwriter." Mr. Simon responded with similar facetiousness, "As soon as he got a chance, he moved up, hierarchically, into more elite buildings." Now these improbable former neighbors are about to become unlikely tour mates. On Tuesday, Sting and Mr. Simon are to announce that they will appear together on a North American tour, during which they will perform several of their best-known songs individually and as a duo. Eighteen dates are scheduled from Feb. 8 through March 16, with additional dates expected to be announced...