Well it is possible, but you will need to ask your server admin for help. A sort of workaround I would call it. There's an app that is installed on the server side. It syncs up specified public folders with users' mailboxes. Then, after the public data is pushed to a private folder, you can easily view it on an iPhone by means of Exchange Active Sync. See this:
Hope this helps.
There is another option available. Here is a blog posting about an enterprise software product that will sync a public folder to multiple exchange mailboxes.
The public folder contacts can be pushed to the main contact folder, or a subfolder. In either case, the contacts will then sync to the iPhone using Exchange Server ActiveSync.