Without a data plan a BlackBerry is useless for it's PRIMARY PURPOSE: email.
That's been the focus of BlackBerrys since day 1. Of course you can use the phone on a pre-paid SIM. You can use any unlocked phone this way. And you can use the PIM features with no SIM at all if you want, just like a Palm Pilot. Terrible waste, however. And there are much better choices for a device if all you want is a calendar and address book.