If you delete it, it might be re-imported by mistake by any random mapper believing there is a building missing here.  That would create nonsense, this  is why we keep it, with the official ref code, but put a "lifecycle prefix" (razed:*) on it so that this is clear the building isn’t there anymore, it won’t be shown on the public map and that would prevent people from believing there is something missing here.

We retag it as long as UrbIS refers it like this.  In a few weeks or months, they will release a new version, with the new building—with a different reference number—and that way we’ll be able to draw it.

Happy mapping.