I can't tell you what the exact percentage is in Ontario. It does happen. There's certainly a crown policy manual that discourages it. It can only be done in certain situations with the approval of either the acting crown attorney for the jurisdiction or the deputy crown attorney.
It's primarily done in situations where there is a great risk that charges are going to be thrown out because of a backlog in courthouses. Those are the jurisdictions in Ontario where you're seeing it most. It is occurring in situations where there are significant difficulties with the crown's case, and it's better to get something than nothing.
This law or any law that's going to increase litigation will put more and more pressure on those dwindling resources.