Easement

My lawyer told me that the neighbor next door has a sewer line that runs across the front of my potential property in Worcester. He didn' tell me this until after the Purchase and Sale Agreement was signed. There is no recorded easement for that house. The two parcels had one owner before but the neighbor bought his house in 2007. The only reason they knew the sewer line was there was because the builder for my lot broke the pipe when they were digging. The oldest document I found in the registry of deeds dated back to 1978 but I don't know how long that line's been there. Does the neighbor have the right to leave as is or is he trespassing? Does adverse possesion apply for an underground sewer line?