According to the state of Arizona:
"Before you can register a vehicle in Arizona, you must show proof of financial responsibility. This can be in the form of a certificate of insurance, a bond, or certificate of deposit or cash in the amount of $40,000." Any of these methods, save the first(certificate of insurance), could be referred to as 'self-insurance'.
The law hasn't changed, the argument hasn't changed:
http://www.azleg.state.az.us/ars/28/04007.htm A. A person in whose name more than twenty-five motor vehicles are registered or who is required to comply with the financial responsibility requirements prescribed in article 2 of this chapter may qualify as a self-insurer by obtaining a certificate of self-insurance issued by the director as provided in this section.
B. On the person's application, the director may issue a certificate of self-insurance if the director is satisfied that the person is able and will continue to be able to pay judgments obtained against the person.
C. On not less than five days' notice and after a hearing, the director may cancel a certificate of self-insurance on reasonable grounds. Failure to pay a judgment within thirty days after the judgment becomes final is a reasonable ground for the cancellation of a certificate of self-insurance.
D. A person who is required to comply with the financial responsibility requirements prescribed in article 2 of this chapter may apply for partial self-insurance to cover any portion of the financial responsibility requirements.
Twenty-five vehicles to self insure. PERIOD.