iPhone sync issue with Exchange

My boss synced his iPhone with iTunes and missed a check box. The end result is that his calendar in Exchange is now blank. I assume that the iPhone overwrote exchange with a blank calendar.

He also has an iPad that still has all the calendar information on it. My question is if I sync the iPad will it repopulate the Exchange calendar or will Exchange overwrite the iPad with a blank calendar?

I will of course backup the iPad before I try but just wanted to ask the community before I try it.