You always wanna do that when you run a call-center. Even if the calls end up in the same queue. Besides the prioritization issue, there's a marketing reason:

For example you might have 3 different 800-numbers all coming to the same call-center.

Based on the number dialed you know that the guy on hold is a ZINC client so while he is on hold you play back messages that try to up-sell him to another card but don't try to sell him a ZINC because he presumably already has one.