Following aliases within rewrite conditions

Question

I have the following code:

Alias /shared /home/espire/espire/website/shared/www

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule !\.(js|ico|gif|jpg|png|css)$ /home/espire/espire/shared_index.php

Which should not rewrite files which actually exists on the server. However, if I'm requesting a file which is located whithin a aliased dir, it doesn't see it as an actual file.
So for instance http://example.com/shared/js/lib/flir/generate.php should be mapped to /home/espire/espire/website/shared/www/js/lib/flir/generate.php. Is there a way to accomplish this without adding another RewriteCond?