Protest by large numbers of people necessarily involves civil disobedience, breaking some laws - walking in the street, thus blocking roadways - because there are too many people for sidewalks, and pedestrians don't like getting whacked (accidentally) with signs.
During labour strikes, places of business are blocked, sometimes supply trucks/trains too.
It can be a tough call, but police are generally reasonable if situations are peaceful. It doesn't seem that there are any issues at the Belleville site. In the picture that someone posted, you can see that the plow truck is actually at the barrier, where cars would normally be when a train is going by. And it's on the shoulder, not even blocking the road. (The car seems temporary, was not in other photos I've seen, on the news, etc.)