Blackberry with ATT 3G Sim, would it work?

[Nde]

This could be a stupid question. But I have a first gen iphone that I share my TMo sim with my BB Curve. Don't boo me yet. BB weekday and iPhone weekend kinda deal. I'm about to get a 3G iphone but needs to keep my Blackberry for work reason.

My question is, has anyone or know anyone that share their new ATT 3G iphone SIM with their Blackberry, and works? It theory, it shoud, BB uses EDGE.

Let me know your experience.

Thanks in advance.