I couldn't find any info online on how to collapse/expand the new Live 8 track groups with the APC.
So when I finally figured it out I'd thought I'd post the answer here in case anyone else is having this problem

* Hold down the 'Track Selection' button (for the group channel) for 1-2 seconds *
This expands the group if it is collapsed / collapses the group if it is expanded.
If this is old news to everyone I'd appreciate a link to some other source for this info - AFAIK there's no official info on new Live 8 features as they pertain to the APC40

Cheers,
Dan