The engine behind Interlocked is 100% custom built for the game in C++.
The renderer itself is built using OpenGL ES 2.0, it's pretty similar to WebGL. Since Interlocked has very modest 3D needs I preferred to build everything myself to make things run butter smooth. The renderer is pretty standard and I could have used Unity, but because my own has only the necessary features for Interlocked it was worth the effort/
Does that catalog have to be an app? For an app, you're right, PhoneGap and WebGL don't sound realistic to me at this stage. For the web, HTML5 and WebGL sound pretty good. You can take a look at Flash and AIR - they have good 3D support, you can make pretty GUIs there and it's cross platform.
If you have more questions feel free to ask