The paragraphs you've excerpted are referring to BES and the tools available to the admin. See the glossary at BlackBerry FAQ - BlackBerryFAQ
There is at least one aftermarket application that will monitor data useage on a personal device -- can't recall the name offhand, but it's something like minimon. Take a look at the 3rd party/aftermarket forum. There is also a list of aftermarket applications at the faq linked above.
EDIT: take a look at MiniMoni goes V 1.01.01 and supports 4.1 firmware now