This almost sounds like something where the Jama "Test Groups" could be used. I know the standard way of grouping tests might be by functional area, but could this feature be used slightly differently, by naming the Test Group after the user-groups you have instead? Then the Test Plans might be focused on functional area instead.
Of course, if you are depending on the notification of via the user-group email when a Test Group is assigned to a user-group, then this may not work out.
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