Sorry, for the cross post, but this seems appropriate here:
On a BlackBerry 8700c with no additional account setup (just BB Unlimited and Voice)
Username for APN:
Password for APN: CINGULAR1
For Modem Use (Yes this works too )
Initialization String: +cgdcont=1,"IP","WAP.CINGULAR"
On an side note I did this during my last billing period and It showed up on my bill as used data, however, there was no charge for it.
Hope this helps !