I've created a file named unattend.xml for use with a standard Windows Server 2012 installation disk (ISO file). I've added the amd64_Microsoft-Windows-International-Core-WinPE_neutral and configured the languages here as well as in the SetupUILanguage entry. I've also added amd64_Microsoft-Windows-Setup_neutral and configured a partition.
I'm creating a new virtual machine with an empty virtual hard drive, I attach the installation ISO to a virtual CD and a separate ISO - containing the unattend.xml constructed above - to a separate virtual CD.
Setup starts fine, however I'm presented with the "Enter your language and other preferences" page, just as if the unattend.xml file presented is not taken into account.
Pressing Shift+F10 and checking the mounted volumes shows the virtual CD containing the unattend.xml available, and "type unattend.xml" clearly shows the content. Based on http://technet.microsoft.com/en-us/library/cc749415(v=ws.10).aspx under paragraph "Implict Answer File Search Order" option 5 clearly states this setup should work.
What's going on ? Not sure where to check for logs, since at this point %WINDIR%\Panther doesn't exist...