My son like yours rear ended a car and we too thought the rego covered any repairs on the other persons car, and have found out the expensive way! It looked like he had done little damage but 6 months after the accident ( we thought they had decided rather stupidly to not get it repaired!) he got an invoice for $4200 with 7 days to pay! I disputed it, asked why we were never given the chance to get independent quotes but was advised thats not how it works in Australia. After asking around and looking into the cost of car repairs here we decided it would be more expense and hassle to contest so again from advise offered them $20 a week which they gladly accepted telling him it was a pleasure to have a youngster offer to pay because the majority they have to chase for the debt.
Why has he got to go to court though? Same situation as my sons and other than have to report it to the police and receive a caution for causing an accident there was no further dealings with the police.