All other issues aside. You need a BIS account. That will let you access your IMAP or POP mail. You can run BES and BIS on the same phone.
I do the very thing that you want to do - I have personal and work e-mail on my phone - however, I am allowed to do it.
You could probably set up a BIS acct. for free through your phone's provider.
However you are using data that your company is paying for. So be careful.