Access control for announcement users to view via link
Try Node authorize link.


  Generates link for view, edit, or delete content without login.
  
  Module maintains authorization key for every node and gives additional
  grants (view/edit/delete) to every user (anonymous too) who accesses
  page with correct key in URL. Module offers function
  node_authlink_get_url($node, $op = 'view') for generate absolute URL
  to selected operation (e.g. for e-mail notifications).


Although the module is minimally maintained I used it two years ago and I did the work.

You can generate links that an anonymous user can use to get access to view a node, for example. I think it works with Conent Access, but not I'm not sure. May be you have to tweak precedence.