I can only speak from experience of the procedure that has been followed. A solicitor in England and Wales alleged to have engaged in criminal offences would also be referred to the Solicitors Regulation Authority, I understand. The SRA may decide to suspend their practising certificate, pending investigation and a possible tribunal hearing.
Evidence that has been obtained during the course of the SE criminal enquiry may not be made available to the Metropolitan Police's Professional Standards Department, to ensure the integrity of the criminal proceedings. I have often asked HR department's not to conduct an internal investigation, as it could undermine the criminal investigation.
As with solicitors, if they lose their license to practice, they cannot work as a solicitor lawfully. So it is with police officers who are dismissed, they are blacklisted permanently from any employment with a police service.