Ken, see my reply above.
I just gave them another call, and another person stood by Mike's response. Any external factor that causes a failure is not covered by their warranty.
I looked over the manuals carefully, and nowhere did it say I had to buy a separate breaker. Doesn't matter, they're not covering it.
I just bought one of their breakers, and will install it when it gets here. I hope the system provides a very long life when I get it back, because it will be the last thing I buy from them. If it fails again, it's going in the garbage, and I'll get another Digitrax system--if I don't just give up on dcc, and/or model railroading. It's getting old, having companies do anything to weasel out of their responsibility.