Or you could use CB Auto Actions (latest version) and do a Joomla ACL action based on a CBSubs event for that plan.
To expand on this further please check out the below topic.
www.joomlapolis.com/forum/153-professional-member-support/218153-cbsubs-with-two-user-groups#218207
The topic provides the trigger and conditionals to ensure a specific plan has become active. You can use any CB Auto Action with the trigger and its conditionals. So for example you could use a Usergroup action to add, replace, or remove usergroups as you see fit based off their subscription.
krileon
