I had a house years ago, plumbers were my best friend coming out to eat up all those tree roots from my old terracotta pipes at least once a year. One misguided plumber told me it was my trees. Rather then suck it up and replace all the pipes with pvc, I eventually cut down my two large trees.
Yep, still had problems with tree roots. Seems trees will travel far and wide to seek out those cracked terracotta pipes, so it could have been any neighbours trees.