When talking to Jerry Seinfeld, Bill and Lisa are speaking with the "actual" Jerry Seinfeld not the fictional "Jerry" from the NBC series "Seinfeld." This implies that "NewsRadio" exists outside the "Seinfeld" universe. And it thus exists outside the "Mad About You" universe since a fictional connection exists between the "Seinfeld" and "Mad About You" universes: Paul was subleasing his apartment to Kramer, and George--at the insistence of a girlfriend--was a reluctant viewer of "Mad About You."
With Jerry Seinfeld starring as "himself" instead of the fictional "Jerry" he plays on "Seinfeld," "NewsRadio" exists outside the realm of "Seinfeld." In addition to this, because Paul Reiser guest stars on "Seinfeld" as Paul Buchman of "Mad About You," "NewsRadio" thus exists outside the realm of "Mad About You," "Friends," and "Caroline in the City" because all three are linked to the "Seinfeld" realm..
Jerry "mistakes" Bills (Phil Hartman) first name with Phil, which is the actors real name. Phil Hartman had also been the late night call to Elaine on Seinfeld, in the episode "The Package"