I would assume they are. If so, you can remove the plaster along with the brown/scratch coat underneath by beating on the plaster with a hammer to break the plaster keys between the lath. Don't beat TOO hard because you want to keep the wood lathing strips in tact. Simple enough, but unbelievably messy (make sure you wear a good respirator because the plaster can contain horsehair or asbestos fibers in some cases, and the brown/scratch coat produces very fine dust when it breaks apart). After the sweep-up, you should still have the wooden lath running horizontally on the wall studs. You will need to apply a new brown/scratch coat, and then apply your finished plaster over that(but you probably know that if you've been plastering for 6 years). If you are simply wanting to remove the surface plaster from the scratch coat, I think you're out of luck unless the surface plaster has already begun to separate from the scratch coat on its own (which it had begun doing in spots in my 102-year-old home). If it's still firmly attached to the scratch coat, my experience has been that it needs be removed as a unit clear back to the lath. Good luck!