Romeo
Why don't you have the cabinet carpenter to build the shelves in his cabinet shop with paint grade plywood applied to the back and you can just put the unit against the wall and secure it with a drill and wood-screws into the wall framing and lath. If you want the shelves sunk into the wall, then you need to cut out the lath and plaster and build the shelving into the wall. You will need to build a header for support if you remove any wall studs. Get a structural professional to help you with wall studs and framing. Here are some pictures of a man doing a project in a bathroom with some built-in shelves. You can see the wall studs and you can see the plaster that was pushed through the cracks in the lath on the back of the opposite wall. He used sheetrock to cover the back of his shelvs and hide the back of the opposite wall.