I would have to think that it would help. Just getting the dish as clean as possible helps.
I considered trying RainX on a dish but read that it doesn't play well with some paints so decided not to try it.
Here in the land of we don't need no stinking FM antenna heaters or dish covers.... We typically only have 2 or 3 snow events per winter but I always get several panicked calls when the sat systems go down. Thankfully, few of my clients are using sat music now so they stay on the air but lose news, programs, etc.
I've wondered if it would help fiberglass dishes shed snow by putting a coat of wax on it?