I've tried my Blackberry today. And it can be added via Carrier for the Internet Connection (Blackberry Internet Service provider). My current BB is from Verizon, and the carrier at my local place is XL. So I register the internet access for my Blackberry trough the XL, and register the email from it
Right if you have a regular BIS service through your provider, you can call up your cellular provider and they can walk you through how to get it setup. Generally they have a particular portal you go to and your setup.
The other option would be to look into a BES (blackberry enterprise server), which is more secure. And you would either have to go with a outsourced exchange email provider or get the BES server+exchange server(both run on windows). You also would have to make sure you are on a BES plan with your cellular carrier then as well.