This is an old question, but a few points have been left out of the other answers.
First, to directly answer the question, yes, the System Volume Information folder can contain sensitive data. As Sorcha described, DFS in particular will store files there by default, but so will many other system services and applications. VSS, System Restore, etc as mentioned by dandavis. Most of these applications and services store their data on the System volume (C) or on the volume being backed up by VSS, so your exposure from the System Volume Information folder on volume G is limited to the data on volume G, though most of this can be configured away from the defaults.
However, there's more going on here than just the potential security risk of the System Volume Information folder.
- Having Directory Listing enabled on Apache is a security risk.
- Pointing Apache to the root of your volume is a security risk.
From this perspective, you're essentially expressing concern that someone might snoop around the contents of your closet when you've left your front door open. You can put a lock on the closet, but maybe you should just shut and lock the front door?
On a side note, I'm going to add that it sounds like you're using typical *nix practices, like splitting your website into multiple partitions, in a Windows environment. Windows is great if you need your server to do more than one thing, to integrate with other servers that do more than one thing, or to host a .NET website. If all you're running is Apache web server, you'll find nearly any flavor of *nix to be more secure and better performing.