Specifically looking at the Honda GL1800 motorcycle NAVI units built by Garmin, although it should apply to all Garmin and maybe even all GPS units. Garmin has released a Version 4.60 firmware in Canada and the US which allow the NAVI units to now use NT mapping. Will this same firmware work in European and Australian motorcycles? In other words, does the firmware decide where in the world it recognizes the satellites from, and is this location specific for different lattitudes or longitudes to the exclusion of other locations? I hope someone can come up with an answer before I give someone the firmware with which to destroy their European NAVI. Thanks.

I can't tell you something about your special unit, but generally the GPS system works worldwide and you wouldn't destroy a device with another regional firmware, if the firmware ir right for the unit type. There are only three possible issues with a "wrong" regional version:
1. maybe the firmware comes with regional basemap, so that you have no overview map in big scale for Europe or other continents outside north america. The routing with detail maps isn't affected by this.
2. maybe it has only partial almanac for north america, so that satfix could need longer time outside north america.
3. maybe you haven't all languages, as e.g. european device.
Don't understand me wrong: these are only the possibilities after my Experiences for long years - it don't mean that it has to be so.