Hi Mike, I'm in charge of Esteren Maps development
I don't know Campaign Cartographer 3 as I have never used it, but to sum up things about Esteren Maps, here are some technical informations :
- The app will be online only (the beta is ready but not yet "available for public", we're waiting a little to communicate on this. And the translation to English is not made yet).
- It's based on a powerful and heavily maintained PHP/Symfony backend, with a LeafletJS-based (and overriden) frontend map management, and I developed a big web-service system behind it to provide data and features to the map (markers, routes, zones, but also map configuration, itineraries, etc.).
Full web 
- The coordinates system is a bitmap one: top-left is {0,0} and {5,10} goes 5 units to the right and 10 units to the bottom (bitmap…)
- Map data are limited to markers, routes and zones, and there are small icons for marker types. The rest is based on SVG polygons with specific colors depending on the element's type.
- The map background is made of tons of 128x128px wide JPG tiles, based on a big map painted by Chris (one of Esteren's illustrators) just for the occasion.
I don't know if any of these data types can be injected into Campaign Cartographer 3, so if you have technical informations about this software, it could be good, and the team would be able to decide whether we can provide tools for Campaign Cartographer

(even though I don't think it's possible yet, there is so much work to be done that it would take a lot of time :/ )