My name is Dan and i actually work for Microsoft Customer Service. as far as questions with exchange connectivity to the iphone this is by far the BEST article out there.
How to setup IMAP4 Exchange 2003 email to sync with your iPhone // Monkeykit’s Blog
now as far as the blackberry working and the iphone not i am almost sure there is a specific handshake that the iphone does as i have had many customers who experience the same issue (blackberry works but iphone doesnt) i will look into this a little more and get back to you as soon as i know for sure. but the iphone gets info from exchange in a different format then other devices so i will make sure.
It is also going to depend on the method used to pump exchange info to the blackberry devices. there is something called Blackberry Enterprise Server for Exchange that makes it deathly simple to sync Blackberry devices but NOT iphones. it can also be set up manually so it will really depend on that as well. keep me updated so i can continue to help you to the best of my ability.