Yeah, they are tested. I've got some on a Boxter I'm working on. I also make a set of aztec decals for some star trek ships that I've been selling for over a year now.
The paper is made by Tango Papa decals. It's quite thin and if you're not careful, very fragile. It takes to setting solutions and solvents quite well, but is really only needed over very complex curves. The printing is done with a combination of color laser and ALPS, depending on the color.