In Queensland, the Summary Offences Act 2005 states "A person who is so near a public place that the person may be seen from the public place must not wilfully expose his or her genitals so that the person’s genitals may be seen from the public place, unless the person has a reasonable excuse."
Across the state border in New South Wales, there is no such statute; only a stricter test of obscenity in or near a public place. This doesn't stop NSW cops arresting World Naked Bike Riders every year, but they have to let them go, every year.
So does one commit an offence if one stands in NSW and exposes oneself to a person in a public place across the border in Queensland? This isn't as clear-cut as the stereotypical example of shooting someone across the border, since no offence has been committed by the self-exposer, in the jurisdiction in which s/he is standing. In the shooting case, the offence is murder, not doing or not doing something in a particular place.
Answers: No; if you're in NSW, then NSW law applies and Queensland does not have jurisdiction or Yes; you committed a Queensland offence, even though you were not geographically in Queensland at the time.