Well, they do animate, but on playback/scrubbing they don't update.
I've built a reverse foot rig out of CAT bones, and after wiring everything up to some custom attributes, the CAT bones won't update after being animated by my sliders. I've added the custom attributes with the 'Add Extra Controller' option to the foot control, so the custom attributes are saved with the anim layer, but still no dice.
Am I missing something, or has anyone else run into this? Is this just an issue with CAT? I've notice other issues similar to this and I've gotten around them with Position/Orientation constraints, but I don't have a workout for the wiring issue.
Seems related to this:
http://www.the-area.com/forum/autodesk-3ds-max/3ds-max-cat/cat-linking-bug-in-2011/UPDATE:
It appears that if the foot control with the custom attributes is animated, the CAT bones animated with the sliders using custom attributes will also update on playback/scrubbing. Definitely seems like a bug with CAT...