Restoring Xamarin components

Hi, I'm in a jam. I need to be able to unpack Xamarin components (xpkg) in Team City. Everything works great in VS but in CI it fails.

Here's my stackoverflow:  http://stackoverflow.com/questions/21068646/setting-up-teamcity-to-handle-xamarin-xpkg

Any tips much appreciated. I guess I'm looking for a command line way of unpacking the component.