I've done hundreds of them and it is as Ole says. The emulsion layer is rolled off the print and then mounted on special adhesive canvas and then placed into a drymount press. Because of the thinness of the emulsion layer the print easily takes the form of the canvas and can look like it is really printed on it.
I used to do them when I did color printing but if you wanted one done most professional labs will do them. It's just called canvas mounting.