A good question that I will try and address from both reading and personal experience. I will break it down into three parts, 1, Location from sellers, 2, Location from inclusions, 3, Location from chemistry.
1, Most of my dealings have been with Africa and the following insights come from there. The location of a new deposit of tourmaline is kept secret if possible because you don’t want more miners and the government interested in your find. You also don’t want to attract wholesale dealers, who will tempt the people working for you to steal more and sell it to them. Since tourmaline mines can be as insignificant as a single man’s gravel pit, there is nothing gained by being specific about your location, especially if your just a transient. Now if people begin to name a specific location for tourmaline, then there is another danger. The location has begun to affect price and miners will take material to where they get the highest price or at least say that it came from there. They will tell you what you want to hear and not just about location.
2, I have read about extensive efforts to identify where tourmaline came from threw inclusion. The only significant source of tourmaline that can be identified by inclusion is the Tanzania area at this time. The rest of the world pretty much share the same problems with tourmaline to varying degrees. One additional idea, that might improve your guess work with red tourmaline is the lack of inclusions in Nigerian red. It is seldom match anywhere else in the world.
3, The chemical separation of copper bearing tourmaline from Brazil and Mozambique (Nigeria to a lesser degree) has been of great interest to me. I was fortunate to get aboard the copper express by purchasing unusual colors from Africa before copper was discover in gem quality tourmaline, I sent the GIA. By defining paraiba like and paraiba type along with Paraiba in chemical terms, as well as other features, has lead to the building of libraries of chemistry data for tourmaline that is known to have come from a certain location. (There is also a price difference between the sources of copper bearing tourmaline driving the work) I have sent gemstones, including examples of my Laurellite (My name for a new variety of Elbaite, which is a copper bearing reverse Alexandrite color changing tourmaline) to help build those libraries. I think that the effort to identify copper bearing tourmaline’ location by chemistry has been large enough, that in most cases a leading laboratory can identify the origins of paraiba like, paraiba type and paraiba tourmaline.
Now on a bit of what tourmaline can not tell you. Tourmaline can not tell us its species by color alone. Dravite is not always brownish, Liddicoatite is not always multi-colored etc. Using Namibia as an example since I identify many of my gemstones as Namibian (I was told by the dealer). Namibia may produce some of the best blue, but it is not unique. Namibia also produces many other colors of tourmaline. I have not heard of purples coming from Namibia, but I can not rule it out. Chemical data must be gather to separate tourmaline from different locations with the same color. With Namibian blue and indicolite in general, I don’t believe the work has been done outside of copper bearing blues. I don’t believe it will be done unless there is a premium associate with a certain location.