Neither have I! I haven't been around the garter scene for long, but the few articles I read on it months ago implied that it was python-specific. Vet did say it can affect all snakes.

However, when he was living at my friend's house, she got a Dumeril's boa that he was sharing close quarters with (she mentioned splitting a heat source between the two.) They weren't in the same cage and I don't imagine she would have had them both out at the same time, but I don't know if that matters. I know she got the boa from a reptile show. She also has a carpet python that she's had for over a year, and several of her friend's snakes have been in and out of her apartment.