That sort of area always has an icy snowpack on the trail, as people walk on it and pack it down. I don't know if that helps. There's also another reason that I didn't go to Greyrock too much in the winter: the small parking lot has a mostly shaded area where you have to drive up a few feet. The slope may be icy. So, yes, you might get some icy stuff in exactly the places where you don't want.
Hewlett Gulch has a road and parking lot that should be in the sun. Also, way less mountainous terrain at the trail. Still, might have some packed ice.