I just stumbled on this, and I wanted to mention that they don't always charge. I've called three times, and I have yet to be charged for it. The first time, my dog ate a whole bottle of Deramax. The manufacturers had actually arranged with animal poison control to pay for any calls related to overdose. Poison control was wonderful through this. They gave me a direct number to have the emergency doctor call as soon as I got the dog to the animal hospital. When I took her to my regular vet for follow up the next day, they also spoke with that vet. Even if I'd had to pay the $50, I'd have considered it a bargain. (Especially when compared to the overnight hospital stay, which was over $1000.)
The second time my dog ate an ant trap and the third my puppy ate a piece of nicotine gum. With those two, they were able to answer very quickly and didn't charge at all.
I just wanted to point this out in case someone hesitates to call for a quick question because of the cost.