Private sewer line goes through a corner of neighbours lot

Hi team, looking for some advice on this one. We recently bought a house on a lot that has been subdivided. Well technically I think the original house was split over two lots but the owner we purchased off renovated the original house, and sold off the back yard as a new lot.

The owner of the neighbouring lot just contacted me to say that they are building soon and that the private sewer connection from our house goes through a corner of their lot.

The pipe is unmarked on any BYDA or public searches.

Now I’ve seen their building plans - they aren’t proposing to build over the top of the pipe and we’ve jointly agreed to fund a detailed survey of the pipe to locate its alignment and depth. The closest their building works would get to the pipe is to within a meter or so horizontally (unknown vertically).

My concern is what happens and who is liable if the pipe gets damaged during construction? How worried do I need to be about this and should I talk to a property lawyer? Thanks!