since a couple of days the UM Language Packs for the Service Pack 2 are available for download at Microsoft: http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=9eb9725a-affc-4051-99c7-1936e8c21031

They can be installed with the following command: setup.com /AddUmLanguagePack:<UmLanguagePackName> /s: d:\<MyLocalDownloadFolder>.