I have two B registered cars, It's the same wording on the license as the classic and vintage car guys have for about $60 a year rego but it costs me $479 each
You can drive during an event, to or from an event, to or from a place of repair or display only. You better have a good excuse if Mr Plod sees you driving to work two days in a row. It's a special dispensation for genuine competition cars to remain licensed, some cars have been licensed using this scheme to simply circumvent compliance requirements and are being daily driven. If too many tools get caught doing this they'll more than likely shut it down. In N.S.W. they have a similar set up but with dedicated number plates. You need to ring up a 1800 number and get a permit every time you drive the car. If your car is mildly modified you may be able to get an A class rego with a modification permit instead. Intrusion bars, hydraulic handbrake, pedal box, bag tank etc. are all immediate B rego though.