Como apanhei um pouco, deixo neste post o meu arquivo LocalSettings.php para autenticação via LDAP no MediaWiki.

require_once( "$IP/extensions/LdapAuthentication/LdapAuthentication.php" );
$wgAuth = new LdapAuthenticationPlugin();
$wgLDAPUseLocal = false;
$wgLDAPLowerCaseUsername = array( "SERVER.COM" => true );
$wgLDAPDomainNames = array( "SERVER.COM" );
$wgLDAPServerNames = array( "SERVER.COM" => "SERVER.COM.ip" );
$wgLDAPEncryptionType = array( "SERVER.COM" => "clear" );
$wgLDAPSearchStrings = array( "SERVER.COM"=>"uid=USER-NAME,ou=people,dc=SERVER,dc=COM");
$wgLDAPBaseDNs = array( "SERVER.COM" => "dc=SERVER,dc=COM" );
$wgLDAPDebug = 99;
$wgDebugLogGroups["ldap"] = "/tmp/debug.log";
$wgMinimalPasswordLength = 1;
$wgShowExceptionDetails = true;