[eluser]Mike Ryan[/eluser]
Could you describe the steps you would take to manually download the log files? And the make/model of the web card/AC device if possible? It might be better to write a script to download all of the log files and then feed them in to the database, rather than trying to achieve this within CI.
I am currently doing something quite similar - a perl script (called from cron) downloads log files from external servers at regular intervals and writes the logs to the DB.
Whichever route you choose, you will need some VPN client software to initiate the connection, a method for transferring the files (FTP/SSH/?), and some code to parse the log files in to your required format. If you post specifics about your environment I'm sure someone will come up with something more specific. Like dcunited08 says, SSH would be the perfect solution as it allows simple, secure file transfers via SCP.