The outer border and shadow appears to be from the default window decorations, which I expect they'll remove in some non-app-specific method. The top bar is the standard window headerbar, which they'll probably remove as well, at least for the dialer screen. The gradients are part of the default GTK theme. Not sure about the button labels, as it's been a while since I touched GTK development - there may not be an easy way to add labels under an image in a button.

EDIT: designs almost always look nicer than the first pass at implementing them, as designers can put pixels wherever they want to make things look pretty, while developers are constrained by the technical restrictions of the frameworks being used.