Agreed, I am fairly sure this is not really a FF problem it is just exploiting the fact that IRC is a text protocol and will interpret anything that is sent to it from any program that connects to it .
Surely it doesn't take a hacker to figure out that they didn't receive the money, or did the machine try to fake some sort of error to throw people off? And are not most ATMs just PCs running some software on top of XP?