I work with someone who had a root canal and saved a tooth he was sure he'd need to have pulled. The guy was certain. So who knows.

In theory, they could probably saw off the chain stay and build a new one to attach. It's probably fixable without doing all that, but the real question is what it'll cost. You don't have a photo of the damage, by any chance? I doubt anyone in here can get you a quote, but it'll at least be interesting to look at.