Do commercial airlines have procedures for evacuating pets from the cabin in an emergency? I recently got into an offsite discussion about flying with pets in the cabin and what would happen in an emergency on board. I brought up the fact that United Airlines' pet policy states, "In the event of an emergency, oxygen service will not be available for pets." Southwest has a similar phrase in their pet policy, though I couldn't find anything similar in American Airlines' or Delta's pet policies.

Beyond oxygen service, I was arguing that if an evacuation took place, I wasn't aware of any procedures for getting a carryon pet evacuated safely. I said that the human lives of the other passengers on board would take precedence over a pet. To my knowledge, pets in carriers are essentially treated as a carryon bags in the cabin. I also hypothesized that letting a pet out during an emergency could be extremely dangerous and would likely invoke the ire of the crew, if not get you into legal trouble.

TL/DR: The discussion left me wondering are there actually any procedures for getting carryon pets out of the cabin in an emergency? This is mostly directed at pets that would be in a small kennel and stowed for the duration of the flight under the seat in front of you as a personal item. Are they considered carryon luggage, which should then remain stowed (as awful as that sounds), or treated like infants? Have there been instances of serious accidents where carryon pets were also evacuated in the past?
There are no policies because pets are technically cargo/baggage as you note in the question, and treated as such. In other words in case of an emergency evacuating the passengers is a priority and as you would be instructed to leave your baggage behind you would more than likely be instructed to leave any pets behind.  


  The Federal Aviation Administration (FAA) allows each airline to
  decide if they will allow you to travel with your pet in the passenger
  cabin. If an airline does allow you to bring your pet into the cabin,
  we consider your pet container to be carry-on baggage and you must
  follow all carry on baggage rules (14 CFR part 121, section
  121.589)


The exception to this is service animals which are not treated as pets. 


  Service animals are not pets. They are working animals that assist persons with disabilities.