This is probably a “cannot see the forest because of the trees” situation,
but how do I create a script which does the automated import of Posts/Pages, without a hook in the WP Website-GUI (e.g. in Theme’s functions.php). It should be standalone triggerable by calling the script name via webserver.
via this API-call wp_insert_post()
You want to use the WordPress API (http://codex.wordpress.org/XML-RPC_wp) to connect. You can do this with almost any scripting language, but since you mention running it on the webserver, and WordPress is written in PHP, we’ll go with that language for now.
Check out this tutorial:
http://life.mysiteonline.org/archives/161-Automatic-Post-Creation-with-Wordpress,-PHP,-and-XML-RPC.html
He shows example of how to create a script that will insert a post into your WordPress blog. The script can be given execute permissions and ran via the command line or a cron job.
You will have to code the logic to get the post from wherever your data is stored, though.