I think I may know the answer to this one already...
It is my understanding that the racers give their passports to production, who obtain multiple Visas, some for the countries to be visited, some as "decoys". So yes, when their passports are returned to them, they can see visas for a group of countries, but they don't know which ones of those countries will actually be visited. So they have an idea based on the possibilities, but they don't know exactly, if that makes sense? But I will be glad to ask to be sure!!