In another question about NASA test of asymmetric thrustor, the published data suggested a possible force interaction of the device with some stress energy field that was moving about the same velocity as Isotropic CMB. One necessary condition was said to be that the CMB would need to have a curl free component of stress energy.
Argument could be made that some of the microwaves cancel out EM components by interference, leaving a curl free stress energy component that is scalar in the Isotropic CMB, but vectored flow of stress energy and momentum compared to any object like the solar system that has a velocity relative to the Isotropic CMB.
CMB with curl free stress energy field does not guarantee any interaction in the NASA data, which faces other challenges. It would create the possibility that some other field generator could achieve efficiency about 1000 times better than a photonic engine. This is still not my preferred energy field for interaction with a quantum thruster, but raises possibility of a technology that is not well researched.
Does Isotropic CMB Have A Curl Free Stress Energy Component?