I have a highly ranked traffic cop and a good long term mate who is training to be a traffic cop at the moment.
The rules shocked me a bit! Police can do ANY speed they want IF the conditions are not putting any other road users lifes or safety at risk, under the condition that they have NOT engaged lights or sirens. They may do ANY speed to get to you, but once they engage/call through a chase, it's a maximum of 40km/h over the legal speed limit.
Had my fair share of Police chases. Stupid stupid days. I've realised how f**ken much of a tool I was!