There are CCTV through Bundaberg town and surrounds, including Gin Gin. I don't know the area to map them, or understand the route into Bundaberg from Gin Gin (or to the state forests they have been searching), but I would be confident the car has been seen on the Council CCTV and possibly shops, residences, service stations etc. That supports that the police know the car was heading to the airport and in the vicinity of Airport Drive (not covered by CCTV) and likely tracked back through the town, giving them an idea of any time 'gap' between movements away from the airport, back home to Gin Gin and then...
What the CCTV might not have shown is if PB was in the car, keeping in mind she had recently dyed her hair the same colour as TB. Hence, the requests for dash cam footage to determine what happened on Airport Drive, but also the car occupants.
I think the BF call is solid, there is no reason for him to lie, and there would be evidence of the contact on his phone. Given that it is consistently referred to as a call, I think it wasn't a text and he heard her voice. If he heard her voice around 8.30am, then she was in the car somewhere near the airport.
A few people have mentioned waste tips, I don't know what tips are in Bundaberg and Gin Gin but there are some waste management CCTV sites (these might be tips?).