Pork tenderloin was put into hot oven which was accidentally turned off for 1 and 1/2 hours. Was it safe to finish cooking?
I don't think anyone will want to tell you that your meat is definitely safe, but there are a couple of factors that lead me to believe you're just fine.


It's generally recommended that pork be cooked to 145°F. However, that doesn't mean that at 145° suddenly all the bacteria die at once. It's actually more of a curve, so the longer the meat is at a particular temperature the more bacteria will be killed. You can sous vide pork for at least an hour at 130° and it will be safe to eat. 
Because you cooked it to 180° (well above the necessary temp to kill bacteria), you surely killed off everything and its brother. The risk factor is going to be instead any toxins created by the bacteria during the time it was in the "danger zone" of 40°-140°F, which in your case probably wasn't very long.


Other factors that will come into play is how the meat was handled and stored before cooking. Was it flash frozen by the butcher? Did it ever thaw and then refreeze? Was was the health of the animal before it was slaughtered? Also very important: you say it was partially thawed. Do you buy it frozen and then partially thaw it in the fridge or on the counter (you should thaw in the fridge)?