Do commercial airlines have procedures for evacuating pets from the cabin in an emergency?
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.