email with sim card not on your regular network

Hi,
Hope this makes sense. I have an unlocked Blackberry 8700r on Rogers. I plan to be in Florida later this year for a month and would like to use perhaps a AT&T or T-Mobile sim card while there. I presently have 2 shaw cable emails forwarded to my Blackberry. Is there a way to still receive them? T-Mobile says they give you an email [email protected]. Could I forward the shaw email to the tmobile email and would it show up on the blackberry?
Or does anyone have any other suggestions.