I work on the principle that if they are using cold calling to sell it then, firstly, not enough companies are taking up the advertising space naturally, which says something, and secondly, that it is probably over priced to pay for the cold calling.
Having said that I have no direct experience of whether this particular deal is good or not.
I would ask the sales people. Surely they would be able to give you a rough idea of what previous CTRs were.
Maybe you could enter into a short term contract (like a month) with an option to extend for a greater period of time, to trial it. See how creative the sales person will be, in order to secure your bussiness.