Attila and Warhammer appear to be using entirely different techniques.
This is presumably as Warhammer's siege, underground and ambush battles maps aren't linked into the main campaign landscape? I note he says that land battles aren't handled in that file, as they'll presumably still be handled in the tile_map.tiles file (which Attila uses for both land and siege battles).
I've already built a tool to modify the file for Attila, it's just as-of-yet unreleased (except to the AE and MK teams). I'll release it eventually but there's a few things I'd want to add to it and do first.