IIRC all your custom POIs are stored in a single file, so if you add your own POIs for more than just your guild hall then those would be shared as well if you share that file.
The files are XML so you can edit them to make a version that contains only your guild hall's POIs by removing your other POIs. Of course if the folks you are distributing that file to already have their own custom POIs they will need to manually merge yours in or just use your file.
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