Hey there,
Since Hotspots is a hosted solution - which means you hosted on your own server. It doesn't really make sense for us to create a custom exporter. You have access to the data -> it's stored in the mysql table.
You can export the locations from the #__hotsptos_marker table.
The problem are most probably the categories. WE use the joomla standard category table. So if your other site already has categories the category ids would most probably collide. You'll have to handle this with a custom script. You can for example create the categories manually -> this way you'll have the ids, and when you do the import you can then match the catid from the old site to the new site.
Kind regards,
Daniel