Yes. And a plasma will emit a lot of black-body radiation in the infrared range (heat). So hypersonics should be track-able by this system.

BTW, my understanding is that the Russian hypersonic systems are quite primitive - they are merely trans-orbital rockets. I.e., they are not scramjets. That means that they have a boost phase, and after that, their maneuvering is limited to a narrow range along their original trajectory - they can't completely change course and go somewhere else.