Runner, you forget that the internal organs aren't the only valuable bits of a human body. Ghouls, Wendigos, and others eat the flesh. Bones, skin, and muscle can also be transplanted, especially in less well off areas where synthetic copies are hard to come by. By the time Tamanous is done with a corpse, while a Shedim could possess it, they wouldn't be happy since it would be unable to actually do anything in that lump of medical waste.
And just because cemeteries are protected does not mean Shedim need any help finding bodies to live in. The morgues are always full of bodies, and there are plenty that never make it to the morgue. If anything, I'd think that Tamanous would be against having the Shedim around, because they steal potential profits from them.