BlackBerry browsr uses BES for surfing and intranet access, cant change that.
Are you with OS5 and older devices?
If yes set to devices default browser to internet Browser and add to favorite the intranet sites you need to open in BlackBerry browser by default in the properties of the link on device. (been a few years since doing so)
OS 6 and 7 use wifi and then Carrier by default KB23699-Simplified browser selection in BlackBerry 6 and BlackBerry 7