The short-ish answer is: I do not believe that FormsPublisher provides the ability to hide tabs.
..at least not in any supported way. The closest you can get without a JS hack is to wrap the content of the whole tab in a container, and then hide the container when appropriate.
I didn't think you could put a tab in a container - at least not according to the DTD, and then (also according to the DTD) container's don't support the hidden sub-element, though I suppose you might be able still do that with FormAPI (haven't bothered trying)
I said wrap the content of the whole tab container.. meaning a container would be the immediate child of the tab element. Then when you hide that (with FormAPI), the tab is still there but it'll be completely empty. Close enough I say.
Yes this is a valid scenario. But the tab will still be visible right?