My guess is that one of two things will happen when you pass a mile marker.
a. One person will call out the time and then the pace and then the time and then the pace ad nauseum. If iI were the one calling, I would have to have a chart to help me instantly calculate the pace, especially at mile marker 18 for example.
b. Two people at every mile marker, one calling out time, and the other calling out pace. Most likely one person will call off the time every 5 to 10 seconds. Somebody else will be calling out the pace every 15 seconds and reading off a chart. When the time caller says "20:30" at mile two, the pace caller will say "10:15 pace."
While this may sound like an interesting idea, it never help me much. The time calling is based on you starting at the front of the pack when the gun goes off. I don't know about you, but that doesn't happen for me. I'm usually 3 minutes behind. Sometimes that's because I start in the back of the pack with my pace group and sometimes that's because I'm in the portapotty when the gun goes off. Thank goodness for chip-timing....
If you are interested in your pace, wear a watch. When you hit a milemarker, you can calculate your own splits. Besides, you've got 7-12 minutes (approx) to do the math before you hit the next mile marker...