Looks like it's closed source so you'd need to ask the app developers. It does look rather cool though - nice to have a single app that can combine multiple sets of overlay data.

I wonder if we could reverse engineer the layer data and write our own app to do this (obviously no compass is a pita, but proof of concept and all).

In fact it might not even need to be reverse engineered as there's a developer page here: http://layar.pbworks.com/w/page/7783228/FrontPage