The reason every NBC station has a different show at 10:30 pm is because NBC gave the time back to the affiliates that season. Groucho moved from 8 pm to 10 pm in 1958; the shows which followed him were "Masquerade Party" in 1958-59 and "The Lawless Years" in 1959-60. Apparently, neither set the woods on fire, and Groucho's ratings were falling as well by 1960-61. I guess NBC decided it wasn't worth it to program 10:30, even though the competition was hardly formidable: Ernie Kovacs' "Take A Good Look" on ABC and "The June Allyson Show" on CBS.
Although never listed as an ABC secondary affiliate, WSPA (CBS) did pick up a few network shows pre-empted on WLOS. "Harrigan and Son" was one such show (it was on ABC Fridays at 8, when WLOS ran movies), "Take A Good Look" was another (Tuesdays, I believe), and WSPA continued to pick up an occasional ABC show until 1968; "Treasure Isle" was the last ABC show I remember being on WSPA (airing at 9 am instead of the recommended time of 12:30 pm, when "Search For Tomorrow" and (until September) "Guiding Light" were on CBS. At that time, WSPA dropped "Treasure Isle" and aired "Art Linkletter's House Party" on delay from 4 pm ("GL" got Linkletter's traditional 2:30 slot when it went to 30 minutes).
Although never listed as an ABC secondary affiliate, WSPA (CBS) did pick up a few network shows pre-empted on WLOS. "Harrigan and Son" was one such show (it was on ABC Fridays at 8, when WLOS ran movies), "Take A Good Look" was another (Tuesdays, I believe), and WSPA continued to pick up an occasional ABC show until 1968; "Treasure Isle" was the last ABC show I remember being on WSPA (airing at 9 am instead of the recommended time of 12:30 pm, when "Search For Tomorrow" and (until September) "Guiding Light" were on CBS. At that time, WSPA dropped "Treasure Isle" and aired "Art Linkletter's House Party" on delay from 4 pm ("GL" got Linkletter's traditional 2:30 slot when it went to 30 minutes).