I just bought a brand new house with a roughed in bathroom in the basement. I have a new toilet, pedestal sink, and shower stall. There is a pvc pipe coming up from the concrete that I assume is for the shower, there is a square piece of plywood embeded in the concrete that I would think after it is removed would be where the toilet is installed, and there is a drain line with a vent for the sink. Is this correct?
Usually when there's a boxed, opening in the concrete, it's for the shower/tub, since they require a trap inline. And they are not all exactly the same dimensions for each unit. The toilet will be a 3 or 4 inch pipe coming straight up from the concrete, usually surounded by a 3/4 inch (or so) layer of foam, to be torn out so the flange can be installed over it.
If you can, check with some neighbors and see if they've finished their basements. Hey... can't hurt!!