[WillPS]

Ah - given that this was the 90s, I assumed it was Batman: The Animated Series, not Adam West's then 30 year old show. It's highly unusual for a kids channel to air something so old.

Not really, especially back then. Cartoon Network also showed Thunderbirds in the early 00s, and Nickelodeon had showed a number of supermarionation series including Joe 90 earlier in the 90s. 

Cartoon Network was still showing Taft cartoons from the 70s back then too, as was anywhere else who had the rights to them (CBBC). 

Not really that different to airing golden-era Simpsons series today when you think about it.

More recently you had the nightly Nick Jr Classics strand too which showed old content.