Role based access control for private chats

Would it be easy to have Taxonomy Access Control control the access to chats?
I thouht i would work right away, but didn't. Anyone knows what should be done?

I'll explain how I got chats only accessible to certain roles. The solution is certainly not perfect, but I don't know how to do it better, and it just works. It's a solution for my particular case.

First - hook_access in chatroom always return TRUE or FALSE, which doesn't allow other content access control. I just replaced two functions:

  function chatroom_chat_access($op, $node, $account) {
    return NULL;
  }

  function chatroom_access($op, $node, $account) {
    return NULL;
  }

What's important in this replacement is to delete the 'view' permission, but in my case I could just delete everything.

This leaves all control to TAC. Just add Chat Rooms and Chats to a Taxonomy vocabulary, assign each Chat Room and Chat a (or many) taxonomy terms, and specify in Taxonomy Access Permissions the rules.

Second - to show in a Chat Room list only the Chats that can be viewed, I added in hook_view:

  function chatroom_view($node, $teaser = FALSE, $page = FALSE) {
    // ...
    foreach ($node->chatroom->chats as $chat) {
      if (node_access('view', node_load($chat->nid)) == FALSE) // ADDED
        continue; // ADDED
    // ...

This skips the visualization of chats which can't be viewed. I don't think this is quite efficient, because it has to load each chat. This can't be done in hook_load because it causes an infinite loop of loads. Maybe it could be done more efficiently only accessing some node content (Views does it) but I don't know how this could be done.

I think something should change in the module to be able to do this by default, but some research should be done to find the cleanest and most efficient way of doing it.

Looking at preliminary testing, Victor's solution worked for me. I wasn't having an issue with Taxonomy Access Control, but with UC Node Access. After purchase customer's were still not having access. After replacing the hook_access functions, content access started working as it should for the chats.