As a producer I would be happy to share that information with my other clients but only after the purchase was made. As a client who is paying a premium price for semi-exclusive content I wouldn't make the purchase without knowing this information. A producer who refused the info would throw up red flags as to how many licenses he was actually selling as compared to how many he claims to be selling. Also if I ran across said content on another site I would then know whether it was there legally so I wouldn't waste your time contacting you every time I saw the stuff.
BTW, it's 'prospective'.
