In short, if a battery is not listed as Protected, then it is not. The AW IMR batteries Rob recommends for our REO's are not protected. That is not to say that they are dangerous. A Protected lithium ion battery has a circuit board, typically in the base to guard against shorts, overcharge, overdischarge and overheating. They are also slightly longer to accommodate this circuitry. A not Protected lithium ion battery still has a veristor just below the button top that will sacrifice itself in the case of a short, overcharge or overheat condition. Similarly, a not Protected battery, if too overdischarged, is usually toast, whereas the Protected battery will shut down before it reaches that terminal point.
The truth is, both styles are quite safe. The major causes of battery failure are human error and failed chargers. I test mine when they come out and before they go in. I change my batteries several times a day. My I-4 charger sits in a heavy pyrex pie plate with no combustible materials close by. (ie, lampshades or curtains) I also installed a smoke detector in that room. That's it! Take the basic precautions and don't think any more of it.