Think this was a bug as mentioned by Dark thinking it worked before.
Snow Layers only clear with break blocks on. I find this odd since something like snow isn't considered usually a normal block, and for features like a server having break blocks on can be a huge issue.

I guess the best way to describe it would be simply turn off break blocks and drive any locomotive over deep-snowed tracks.
Maybe this is an intended feature and I'm wrong but I whipped up this quick thing as instructed so the team can look into it.
Thanks guys.