Take this url:

http://example.com/info.php/some%20url

to be some standard <?php phpinfo ?> page.

Using mod_php this will show:

_SERVER["REQUEST_URI"] = /info.php/some%20url
_SERVER["SCRIPT_NAME"] = /info.php
_SERVER["PATH_INFO"]   = /some url

Using mod_fcgid/mod_fastcgi it will show:

_SERVER["REQUEST_URI"] = /info.php/some%20url
_SERVER["SCRIPT_NAME"] = /info.php
_SERVER["PATH_INFO"]   = /some url

However using mod_proxy_fcgi it shows:

_SERVER["REQUEST_URI"] = /info.php/some%20url
_SERVER["SCRIPT_NAME"] = /info.php/some url
_SERVER["PATH_INFO"]   = /some%20url

So unlike the other modules mod_proxy_fcgi seems to not decode the URL.

(using the ProxyPassMatch rule from apache wiki)