question about acl and readmore

hello, i will give a try to explain my problem/question...
We have a site with about 5 article categories (for ex cat1, cat2, cat3,..). We have also several usergroups (f.e. usergroupA, usergroupB and usergroupC). They are all registered groups (so no author rights or something else). We want all usergroups AND public users to show the introtext in all category blog views. But only usergroupA may see a "readmore" link for the article categories cat1 and cat3, while usergroupB can see the readmore for cat3 and usergroupC has to be able to read the full text of cat2. (these are all examples but i can't better explain what we want to reach.
I suppose this is not standard with joomla 2.5.6? We use the last version of CB. Do we have to purchase CBSubs to reach something like this or are there less difficult solutions?
We have also the same problem using DOCMAN 1.6.
Any suggestions?

CBSubs has no relation to usergroup usage. What it can do is protect an article from being viewed by anyone except those subscribed to a specific plan. You can then configure it to show the intro and only protect the readmore text.

As for doing this with just Joomla you'll probably need a 3rd party content extension like K2 to manage your articles and add new features. Aside from that you may want to post your question to Joomla.org for best suggestion.

For DOCman we use DOCman groups. Then simply apply said group using our CBSubs DOCman integration. We then assign downloads to those groups. This gives us download access permissions based off subscription. No relation to usergroup usage.