This is very interesting. I don't want to install Freeware on a corporate server but if this VB or C# app can do it then maybe I could do the same. If I could find something open source that is similar I could see how to do it.

I did some more snooping around and found unlocking-files-that-are-in-use. The article actually mentions unblocker and shows how to unlock a file with Microsoft's Sysinternal process explorer tool. I don't know if there is a command line interface to this or not, but looks certainly like something worth more investigation. I presume that your company would not have a problem with freeware from Microsoft's technet.

I still was not able to find the underlying mechanism that these folks use to perform the unlocking - but evidently enough folks have figured it out that with more effort, this could be discovered. I hope that the above tool can be controlled via command line and if so, then I think you are in good shape.