Visual Studio 2012 introduced VSTest.Console.exe to replace MSTest.exe.

See here for more information:
http://msdn.microsoft.com/en-us/library/vstudio/ms182486.aspx

For the most part the trx output format is the same, except the class name is no longer in the full assembly reference format. It is now just the class name.

MSTest.exe:
className="Foo.AssemblyName.Namespace.TestClass, Foo.AssemblyName, Version=1.0.0.0, Culture=neutral, PublicKeyToken=0123abcd0123abcd"

VSTest.Console.exe:
className="Foo.AssemblyName.Namespace.TestClass"

Attached is a modified xsl that addresses this difference. Please review and incorporate at your earliest convenience.