Quote - The OP did not state the reason for asking about this projection mode. So perhaps I'm off-base in assuming the actual goal has nothing to do with projection modes, per se, but rather the goal is to integrate a 3D object so that some elements of the photo appear to be in front of the object and others appear to be behind.

I don't know what the OP wants either but that's not the main use of camera mapping. Camera mapping is a way to take a 2D texture/image and by projecting it on dummies, make it appear to respond properly to camera motion. This way you dont have to make a fully textured 3D object for everything in a scene but can just do a nice detailed matte image and use cam mapping to fake the rest. It sees extensive use in film work where most of the backgrounds you see (like the cities in the star wars prequels or the environments in LOTR) are done this way.

To show a simple example, start with a photo of a box:

Import to your app and match it with a dummy cube:

Apply a camera projection on the dummy and try a render. Right now it matches the original photo:

But since its actually projected onto a 3d object, we can now move the camera around like this:

Now of course you could have created a 3D box, textured it to match the photo, then setup lighting to match, but it would have taken far longer then what i just did in 5 minutes. There are also artifacts because the source image is low rez and you're limited in the kind of cam moves you can do, but it saves so much time for complex backgrounds that its more then worth it. It's a pity we don't have proper support for it in poser, as it's one of the most powerful CG techniques out there.