This is unrelated to permissions. Weather something can be seen or not is controlled using an access context. https://rsjazz.wordpress.com/2016/01/27/manage-access-control-permissions-for-work-items-and-versionables/ discusses the various options.

The only with built in automation is to set the access context/restricted access based on the category. And that basically does not work as you describe above. If access to work items is limited by category, only members of the team area can see the work items. Users that should see everything must either be members in every team or have the JazzAdmin repository role.

You could use access groups and some custom automation. You would create three access groups a,b,c and add the team area of team b to group b and of team c to group c. The team area a is added to all access groups. Your automation would set the access control accordingly. This should have the effect you want.

Hi Heather

From your query, I think you are looking to restrict the category visibility and the work-item access for the particular teams.

Define the categories that work items are filed against, and associate categories with the team areas responsible for those categories. The team area associated to the top-level category is the default team area used when no other team area association takes precedence.
Each category can be configured to be visible to members of the team only (Restrict Category Visibility). In addition, each category can be configured so that work items filed against the category are only accessible from members of the associated team (Restrict Work Item Access).

Perform these steps in the RTC web client.

You can refer this jazz article too for detailed information:
Using the Work Item Access Restriction feature in Rational Team Concert

At Project Level, Set the Project Area access control to, at least, the Members of the project area hierarchy.

If this answers your question please mark it as accepted.

Regards,
Rohit