About the 1984 NBC Reruns

During the summer of 1984, owing to the newfound success of its star Tom Hanks in feature films following the release of Splash and Bachelor Party, NBC briefly reran episodes of Bosom Buddies to lead off that network's Saturday night line-up.

The only reason I'm starting this thread is to ask this question: If Bosom Buddies had aired on ABC, then how did NBC get the rights to rebroadcast the sitcom that summer?