Assuming the conditions are met, what are legitimate costs? First, California law does allow police agencies to recover costs associated with an "emergency response" to a DUI related incident. Courts have given broad meaning as to what constitutes a recoverable cost, for example, one recent case found that, An “appropriate emergency response” to an incident includes the cost of providing police services at the scene, including, among other possible items, salary costs related to ensuring public safety at the scene of the incident, obtaining appropriate medical assistance, removing vehicles, investigating the cause of the incident, conducting field sobriety tests, and if appropriate arresting and detaining the subject.
Reimbursement may also be obtained for time spent away from the scene by responding public agency personnel, provided the response is reasonable and arises from the incident. Thus, for example, salary costs may be recovered for time spent traveling to and from the scene, transporting the subject from the scene, booking the subject, performing chemical tests, writing customarily required reports (including all accident and DUI-related reports that must be completed as a consequence of the incident), and performing follow-up investigation necessary to complete the reports. The case is Allende vs. CHP.
But what about costs associated with a simple stop for a non-accident, say where the driver was pulled over for not using a turn signal and that evolved into an arrest. In this instance, the law may not allow the city to get reimbursed for the officers time. Bottom line, if an accident occurs where there is a collision with some other vehicle or object and the police are dispatched out, you may be on the hook for payment. This does not mean that you cannot negotiate with the agency for settlement. I advise people to send a letter responding to the request, disputing payment of the amount first. Then, state that you are offering a reduced amount as an accord and satisfaction of the disputed debt. Write "payment in full" on the check and send it along with the letter. Write "please see attached letter" somewhere on the check. A good target for compromise may be 50 percent of the requested amount but you are free to negotiate whatever amount you wish.
One final thing. In the event you do nothing they may pursue the claim in civil court, it has no bearing on the criminal case and you cannot be arrested for non-payment. However, they may refer the case to collection and hound you for payment.