[batman1425]

Seems to me you would need to see what occurred first, which may be challenging. Did a foundation failure cause an instability which lead to the pipe breaking, or was the pipe slowly leaking, which caused destabilization of the footings in the foundation.

I'd get an independent 3rd party (not someone that has skin in the game with respect to existing plumbing or foundation) in to try and make that assessment. Either way - you will still be in for fight. Both entities are going to blame one another, and I'm willing to be there is sufficient legal-eese in your contracts that even if you took them to court, you likelihood of success for compensation will be low.