No, they would not be interchangable. blackberry has to go through the BIS to get your emails pushed to your berry. the only way I see to do this would be to have two SIMs and two seperate data plans.
Blackberry's and iPhones are like apples and oranges (no pun intended). Now if I'm wrong someone might correct me, but as far as I'm aware a blackberry data plan is different from that of an iPhone because of the various different apps both run as-well as the operating systems. If I were you I would also call your carrier cos they may be even more knowledgeable of the subject matter.
Posted from my CrackBerry at wapforums.crackberry.com
I am actually running an iPhone 2 (Edge) and Curve 8900. You will need to change your data plan to a BB data plan. The iPhone will still work on the BB data plan but the BB won't work on an iPhone data plan. Weird I know but it is true. All I do now is just swap the SIM card whenever I want to use the other phone. You won't be able to have visual voicemail on the iPhone but everything else works seemlessly. Here is a good link to follow that I used http://forums.crackberry.com/f99/how...a-plan-348311/ Best of luck.