I'm working on our own script to do something along these lines here, but I'm taking a different tack. Instead of every user subscribing to the feed and updating it all the time, we created a single account (we called it "shares"). We create the RSS folder in that account, and then just make it a shared folder to all the other accounts in the system. Then we can update the feed on a set time schedule on the "shares" account...and all users get the updated feed automatically.
The downside is that they can't mark messages as read or delete messages.
Code:
zmmailbox -z -m ACCOUNT syncFolder /FolderName
That will refresh an RSS feed from the command line.
Matt