Once fielded, the only real defense will become placement of assets on reverse slopes, which will be impossible to hit (more so than standard artillery).
Not necessarily.
These weapons will also fire precision guided munitions which can use GPS, Infrared, etc. to hit both stationary and moving targets.
They are not powered in the sense that they have any kind of engine, but their control surfaces will allow them to manuever while airborn and hit the target.