Senior Napier counsel Philip Jensen said while there had been misgivings among lawyers it had reached the stage where it would happen.
"Whether in the long run it is a success or not, only time will tell," he said.
Some were concerned that part of the process was to "cull" lawyers from the legal aid system.
He said if that happened "that type of thing will not be done openly".
"I don't know whether it's going to bear the great cost-savings they seem to think it will," he said.
The Ministry of Justice, in material introducing the service to Dunedin, said independent evaluations found the PDS provided a high-quality service.
It said the PDS also achieved cost savings of almost $1 million in Auckland-Manukau over a four-year trial, measured against equivalent private provision.
There was also no difference in outcomes for clients when measured against conviction rates, but convictions for serious cases conducted by the PDS were significantly lower than for privately provided services, the evaluations found.