Hey GBKDalton, you are right-- I went there today and had an interesting time at the Healdsville Trail parking area-- the road is plowed just past the railroad crossing, but is just a snowmobile trail to the actual parking lot. I got my car stuck on the snowmobile trail, stupidly following a set of tire tracks that had probably done the same earlier. After extracting myself with half an hour of digging (yay for having an avalanche shovel in the trunk), I looked back and saw another car stuck just across the snowmobile bridge. I guess I was the lucky one.
Anyway, to answer my own question from today's experience: If you drive in from Station Road, you can park just past the train tracks next to a "road closed" sign, but not in the actual Healdsville Trail parking lot. If you drive in from the Healdsville Road side, you can park just off the paved road where the snowmobile trail (VAST 7, I think) crosses.