You can, if there are aspects of Sherlock specifically (as opposed to things from just the original Doyle stories) that are re-used in Elementary. Such things would include: Watson's leg wound being psychosomatic; Sherlock being a nicotine-patch user instead of a smoker; everyone's texts saying "WRONG!!" at the same instant; the entire way of illustrating Sherlock's deductions graphically with little arrows and bits of text and so forth...these are all elements of the show Sherlock specifically, and if used in Elementary could be grounds for legal action, especially since CBS (the network on which Elementary will air) once discussed doing an American adaptation of Sherlock with Steven Moffat.