Does CiviRules add/remove a contact to a Group based on Membership starting/expiring
Yes Pete, we have not worked on any conditions for membership status. We never had (and never will :-)) have the ambition of creating all sorts of Conditions. We have created the engine and the conditions/actions that our projects need. However, the engine allows you to create your own conditions and actions quite easily, that is documented on our wiki: http://redmine.civicoop.org/projects/civirules/wiki

Documentation pages on creating conditions:
http://redmine.civicoop.org/projects/civirules/wiki/Tutorial_create_a_new_and_simple_condition
http://redmine.civicoop.org/projects/civirules/wiki/Tutorial_create_a_more_complicated_condition_with_its_own_form_processing
It should be a pretty easy job to add a condition for membership type or membership status.