Yes that's doable. Make a copy of the "CB Groupjive - Stream Notification" system action. Then remove the last 2 conditions. Now add the following condition.
Field: Custom > Value
Custom Value: [var3_type]
Operator: Equal To
Value: 4
Then under the User tab set the following.
Code:
if ( ! preg_match( '/^(groupjive\.group\.\d+)/', '[var3_asset]', $matches ) ) {
return null;
}
global $_CB_database;
$query = 'SELECT ' . $_CB_database->NameQuote( 'user_id' )
. "\n FROM " . $_CB_database->NameQuote( '#__comprofiler_plugin_activity_following' )
. "\n WHERE " . $_CB_database->NameQuote( 'asset' ) . " = " . $_CB_database->Quote( $matches[1] );
$_CB_database->setQuery( $query );
return $_CB_database->loadResultArray();
This should notify all users following the page. To send a notification to every user on the site you should just be able to use a global notification for that, which can be done as follows.
Instead of adjusting the User tab instead under Global set User to Self. Now under the Action tab set User to empty, set Global to 1, and set Load By to By Asset and Owner. That should send a global notification to everyone.