One of the more unusual double-duty announcers I've known about was a guy named Walt Harris. I don't know where he was based out of, or anything about his background, but I do know that in the 60s:
He did the syndicated version of Roller Derby, featuring the San Francisco Bay Area Bombers, featuring Charlie O'Connell, Joannie Weston, and Ann Cavello. In Los Angeles, this was shown every Saturday night. Los Angeles was a very strong territory for Roller Derby's main rival, Roller Games, which featured the L.A. Thunderbirds. They must have reached some kind of detente', because later on, Roller Derby teams started appearing in L.A. against the T-Birds.
At the same time, Harris was the announcer for a Minneapolis-based wrestling outfit. I don't remember if it was the forerunner to Verne Gagne's AWA or not. I do remember that it featured a bunch of wrestlers that I never heard of and don't remember today.