True, the fire dept is not going to risk their lives to save pets, but we have seen many reports of fire fighters resuscitating pets as in this current article:
http://www.wsbtv.com/news/news/national/firefighters-save-four-hamsters-o2-after-fire/nhXrX/Also, when we volunteered for Red Cross, we saw cases when fire fighters entered a burned out structure to retrieve pets that didn't survive. It was heartbreaking to see, but the families appreciated the effort.
The pet alert signs could at least alert them to the fact that animals are inside.