I think you may be able to target them with a little CSS. If you had the CSS Classes for Current User's Groups theme component I think you could do something like this:
.post-hidden {
display: none;
}
.group-trust_level_4 .post-hidden {
display: initial;
}
You may need to tinker with it to get the results you want though, depending on staff trust levels or category moderators, etc