What is the determining factor for ordering a panel with breakers (AIC rating) for HVAC equipment

AIC is Amperes of Interrupting Current and this is usually determined by a third party through the third party's testing program.

I really do not understand your question since the utility gives the reading only up to the service entrance and after that a speciality program like Volts or the good old Ohm's Law using conductor impedence as a basis.

I am thinking the factor you might be looking for would be based upon the utilitys numbers for the service entrance to start with then it is on to the local AHJ who inspects the electric to decide what is the necessary paperwork from the manufacturer that will be needed to prove the equipment is in compliance with the code.

This is just my best guess.