I asked a drain surveyor that same question, and he said he'd never seen a pipe run knocked out of true by even very thick roots -- they just go round them like they were lumps of rock. An exception is when a tree is losing anchorage in the ground and roots may be moving in the wind. He had seen a couple of cases where cameras showed pipework knocked out of true, and in both cases, before they returned to reline the pipes, the sewer had been completely ripped out when the tree fell.
What normally happens is a joint leaks, and the roots seach out the source of moisture, entering and blocking the pipe. However, the tree would never have known it was a pipe unless it was already leaking.