The rest of the pipe is in good condition and the cracked pipe is about a foot long as shown in the photo. I had my neglected sewer line cleaned last year and the cleaner had to use a camera and located the original clean out that had been covered over with concrete many years ago. He recommended that I expose it, if possible. And he recommended a yearly cleaning so he doesn't have to send bushels of roots into the city sewer main. So this the result of trying to maintain my sewer system. I think I can trust the sewer since they've been very fair and thorough with me and is well known in the community. And I expect they will have a simple and fairly cheap repair.
I'm wondering if anyone know a few options for a clay pipe patch up. The sewer cleaners were able to an adequate job of cleaning from the sewer stack base 14 feet further away. They gave me a DVD of the final results. I could also see on the video the area may have indeed been weak. It just sort of crumbled away in layers and there are small roots nearby. I hoping just the one 12 inch gap can be dealt with.

The result is a Y cleanout at floor level, not under 18 inches of concrete and sand.