Both ABC and Touchstone Pictures are owned by the Walt Disney Company, so this appears to be an example of corporate synergy long before GE bought Universal Pictures.
Of course, broadcast networks stealing shows from cable sisters already done very well in children’s television, where cable networks’ most popular shows re-air Saturday mornings on the broadcast networks owned by their parent companies: Nickelodeon shows air on CBS, Cartoon Network shows air on the WB, and Disney Channel shows air on ABC. Not to mention reruns of popular broadcast shows reairing on cable: CNBC has The Apprentice, and USA is practically Law and Order central. Disney also seems to pipe shows between ABC and ABC Family- I believe ABC’s current hit Brat Camp originally aired on ABC Family.
Using your cable networks as a second source can also help if your show is popular (or hopes to be): during the first year it was on the air, reruns of 24 would air on FX. This was probably done since 24’s plotlines are useless if you miss an episode in the middle of the series- the show’s story plays out through the entire season.
However, as brickbacon pointed out, not all shows will appeal to all audiences. Viacom not only owns CBS and Comedy Central, but also Nickelodeon, MTV, VH1, Noggin, Logo, UPN, Spike TV, Country Music Television, MTV2, Showtime, BET, and TV Land. That’s a varied landscape. Some shows may appeal to viewers on more than one station, and they probably do air them on two or three networks. But not all tastes are the same. TV conglomerates do use corporate synergy when they think it will attract viewers- and I imagine it will be a growing trend.