It is possible to method to discover if your server supports mod_rewrite &lifier .htcaccess
http://us3.php.net/apache_get_modules will output something such as the next:
Array (  => core  => http_core  => mod_so  => sapi_apache2  => mod_mime  => mod_rewrite )
Just search for mod_rewrite. You can even write a little function using in_array() to really make it simpler to find out whether confirmed module is loaded or otherwise.
I'd produce a test scenario with the addition of mod_rewrite to .htaccess. There's a good example here.