Toutenrab

I’m answering my own question, I’ve succeded to rewrite an URL to a CDN hosted URL:

function rewrite_url_to_cdn_url($url){
    // check if W3 Total Cache is installed
    if(class_exists('W3_Plugin_Cdn')){
        $w3tc_instance = new W3_Plugin_Cdn();
        $path        = str_replace(site_url() . '/','', $url);
        $cdn         = $w3tc_instance->_get_common()->get_cdn();
        $remote_path = $w3tc_instance->_get_common()->uri_to_cdn_uri($path);
        $new_url     = $cdn->format_url($remote_path);
    } else {
        $new_url = $url;
    }
    return $new_url;
}