Tiling over greenboard outside shower area
I'm getting ready to start thinking about getting around to tiling a basement bath remodel.....I'm probably setting a new world record for slowest remodel pace, but that's fine with me. We gutted the basement bath down to the studs, I poured a new cement shower pan (using the Goof-Proof system for creating a sloping pan - worked pretty well), installed cement backerboard on the three walls of the walk in shower (to the ceiling), and drywalled the rest of the bathroom with greenboard. The floor (outside the shower) is cement and in good shape. I'm planning to tile the shower floor and walls, tile the floor of the rest of the bath, and tile 43 inches up the wall of the bath vanity and toliet, leaving the opposite wall with only a 3 inch high "baseboard" of bullnose tile. My question is - am I okay with tiling on the greenboard (where vanity or toliet will go) or do I need to pull out the half wall of greenboard and replace with cement backerboard? Keep in mind this bath will not get a lot of use.