Yes, it does happen but I don't know how much you can count on it every year. This past April I got a state code discount at CBR, std room, for $99 + tax. I think the rack rate was $189 + tax. I don't remember the time period the code covered but we were there 1st-2nd week in April which was peak time. It seems to me the prior year had some state code discounts also but they were different states.
Good luck.