If they are only popping up when you are composing an Outlook email, then that's the 'history' of Outlook working for you.... I am 99.9999% sure they are nowhere in your Address Book. I have that happen all the time at work - I send emails to all of my BB users, so I can just start typing their name and it will pop up. However, none of them are in my personal address book.
No longer a BES Admin, but it was fun while it lasted!