I have heard yes and no on this question. At my hospital, where I work med/surg and ICU prn, we don't allow cell phones to be used inside the hospital. Last weekend I was asked to check each room to see if someone was using a cell phone. A pt had a recent MI and was waiting for transfer when his tele started doing crazy things. The nurse said she sees those kind of waves when cell phones are nearby. I checked and sure enough, someone had their cell phone on. When it was turned off, the pt's tele returned to normal (not sinus, but normal for post MI).
On the other hand, a friend works at another hospital and the hospital supplies her with a cell phone while at work. I'm assuming that since they have cell phones that it doesn't interfere with their telemetry.
Our telemetry system is brand new, state of the art. So the question is: does it or doesn't it? From my experience, it does. But plenty of people claim that it doesn't. What's your experience?