as far as I am aware it is not possible to force systems into these power-states using iAMT. As this is normally not desirable (the user might be working on important documents etc.).
It should however be easy to enforce this using group-policies, or simply push a program to all systems that performs this.
One that I found is http://www.nirsoft.net/utils/nircmd.html (this is an external website and I cannot guarantee for anything on there)