PHP5.4.0のtraitはfinalキーワードは無視されるっぽい。 ref: http://qiita.com/items/2971

file0.php

<?php

trait Foo
{
    final public static function staticMethod()
    {
        echo __METHOD__, PHP_EOL;
    }
}

class Bar
{
    use Foo;

    final public static function staticMethod()
    {
        echo __METHOD__, PHP_EOL;
    }
}

Bar::staticMethod();

コマンド

$ php -v
PHP 5.4.0 (cli) (built: Mar  3 2012 16:55:36) 
Copyright (c) 1997-2012 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2012 Zend Technologies
    with Xdebug v2.2.0-dev, Copyright (c) 2002-2012, by Derick Rethans

$ php Trait.php 
Bar::staticMethod