With the Basic WP .htaccess rules it should at least be taking you to /site and /anothersite on the WordPress install and driving a 404. However it appears your server is handling 404 errors without passing them to WordPress. You may be able to add a custom php5.ini file with the directive cgi.fix_pathinfo = 1. Alternatively adding this to the top of your .htaccess file could disable FastCGI
Options +ExecCGI
AddHandler x-httpd-php5-cgi .php