No chit chat here, just a quick explanation of how to add a Public Folder Calendar to your GAL in Exchange 2013. The quick answer: Mail Enable the Public Folder item.
Once the Public Folder item is mail enabled you’ll be able to see it in the GAL. Here’s how to mail enable an item using the GUI:
Head to Public Folders > Public Folder > Drill Down to the Public Folder Item (Contacts & Calendars are most popular) and highlight the item. On the right hand side you’ll see an option to add mail settings. Enable it and you’re done. You’ll see it show up in the GAL as if it were anything else in your Address Book. It will look like this when done: