Perhaps with all the underground salt in upstate NY they have not started with the Mg salts on your roads yet. But if they do, those too can cause issues.
In our area they don’t use that much salt, but do spray various Mg solutions on the roads to prevent ice formation. It works on the ice (to some extent), but after a few years people started noticing that the pines on the downhill side of the roads were dying. And the county cut back on the Mg use.
Up here, it was the melt water runoff from the road which caused the problem, not the direct spray hitting the trees. If that is the case with salt too, then perhaps some drainage work to direct road water away from your plants would work better than covering them.