The boxwood plants might or might not be beyond recovery. We can't be sure based upon what we can see in the photos.
The tan foliage of winter damaged boxwood can often be trimmed off and new green leaves will develop. However, when the damage is severe, entire stems may be killed. In that case, what's left after trimming may not be enough to constitute a serviceable shrub.
Go here to learn more and please read the Iowa State University bulletin referenced there: