Yes. If you r company has a Blackberry Enterprise Server (BES) then you will need Verizon to set you up on their Enterprise Blackberry service. If you just plain on using the Blackberry Internet Service (BIS) you can go with the cheaper Blackberry data plan.
The reason for the difference is really the carriers finding two things they can charge people for. BIS attaches to IMAP/POP3 etc.... BES attaches to those AND a corporate Blackberry server.
I hate the way the providers devide it up like that, Tmobile divides it into 3 services somehow. Caused a lot of work for me when i converted 95 users over to their own self-liability plans across their choice of providers.
Ok, that makes sense; and after going to the University's helpdesk, it appears that they support either IMAP/POP for the Blackberry OR if you are on exchange, you need a Server license:
Determine whether or not you need to purchase a Blackberry Server Access License. If your Blackberry is owned by the University and uses Sprint or Nextel, it already has a license and you do not need to purchase one. Otherwise, you must purchase a Blackberry Server Access License. Your department's technical support staff can work with the Exchange administrators to purchase a Blackberry Server Access License for you.
Right now I am on IMAP.