I recently discovered the Utah Avalanche Center Podcast, and in the 3rd episode (over a year old now) someone from the DOT is interviewed. He talks about using these cannons, and how essential they are to keeping the roads open. He also talks about how there's this organization across North America that sets rules for safe use of these cannons. What sucks is that if some accident were to happen due to these cannons, the entire program in North America would shut down because the cannons are "not safe". That would really affect people not being able to get to the mountains.
Given how everyone is a wuss this day and age, it's only a matter of time before this happens unfortunately.