Yeah, this has been talked about before, and unless you are on the adcoms, its hard to answer yeas or no. Its probably safe to say though, that they do not contact every EC contact for each applicant....even each interviewee. However, if you go to the interview and they ask you about a certain EC, and you can't talk about ti, I would not be suprised if they call. Also, if you had like 3 ECs that each took 25 hours a week during the same period, that might start lookng suspicious. So, in short, they probably will call if something looks suspiscious, but otherwise they have better things to do with their time.
Another poster was right, though, no one should care if they call, because one would hope everyone is putting down truthful information.