There wasn't any reason to do that in the 1940s because the Pelham IRT (now the #6) pretty much served the same area.
But the Second Avenue subway plan of the 1970s would have used that route; I think there were plans to redevelop the Harlem River Yards (as housing?), and a new station on the subway would have served that. The northern end of the line would have used the old NYW&B station at East 180th Street. The point of that was so riders from the northeast Bronx could transfer to a fast bypass route into Manhattan.
But the Second Avenue subway plan of the 1970s would have used that route; I think there were plans to redevelop the Harlem River Yards (as housing?), and a new station on the subway would have served that. The northern end of the line would have used the old NYW&B station at East 180th Street. The point of that was so riders from the northeast Bronx could transfer to a fast bypass route into Manhattan.