Some documentation suggests that using Offline Files with read-only networks shares will not work or at the very least is not supported. For example, this could be inferred by reading the following blog post that describes the minimum share and NTFS permissions needed for using Offline Files and Folder Redirection in Windows Server 2008 and Windows Server 2008 R2:
However, the reality is that Offline Files is able to cache content from read-only network shares. That's because Offline Files also caches the effective user access permissions to each file in the offline folder. Of course, if the user's computer is disconnected from the network, they will be unable to open such cached files for WRITE DATA access, but that is "by design" because it's not part of the intended scenario for Offline Files, which is to work together with Folder Redirection to relocate user's known folders to network file servers.
Mitch Tulloch is a eight-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. This tip was excerpted from his new book Installing and Configuring Windows Server 2012 Training Guide published by Microsoft Press which is available from Amazon. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.