I would recommend using the Polygon.ContainmentTest node for this. So get your parcel outlines, get convert them into Dynamo polygons and then run the containment test on the sewer lateral points. The reason is because a Bounding Box is axis-aligned and not element-aligned, meaning that it won’t be truly “shrink-wrapped” to the parcel geometry unless the parcel is perfectly parallel and perpendicular with the world X and Y axes. In other words, the BoundingBox.Contains node might return true even if a point falls outside the parcel boundary. If you want to use Bounding Boxes, you’ll likely have to do some extra gymnastics to get them aligned properly like this example.
A third option, although more computationally heavy, is to patch the parcel polycurves with a surface and then use the Geometry.DoesIntersect node to test if the points intersect with the surface. If they do, then they are within the parcel boundary.