Not all phones on the business accounts at corporations have any capibility to connect to exchange servers, and not all of them are billed to the company. 95% of the phones my company's employees have are under the corporate business agreement (sometimes called foundation), and have no corporate email and are paid for by the employees themselves. Some of us expense out phones, some have phones that are owned and billed to the company. The advantage of the business/foundation plan is that it saves anywhere between 15 and 30% off of the monthly services. I was hoping that AT&T would enable the discount for iPhone plans, as I'm paying an extra 26% to have my iPhone without the discount.
It's not about security, but more about information control. Some companies wish or need, either by internal policy or by financial regulation, to control the information. There is nothing more insecure about imap technology than exchange.
-jt2