When I did this "road" there were a couple of barriers, but you can go around them. Local bikers told me that it's OK. Try not to ride there on a weekend, as there will be quite a few people walking and riding bicycles.
On the opposite side of the Col de Tende there is another gravel road which is open. It will take you to Casterino, where you can do another gravel loop. There are a few interesting looking forts along the way worth exploring. One of them had the drawbridge removed. You have to storm it via an opening for cannons. Bring a torch and watch your step.