they would say that, it is uncommon but not impossible, get an engineer out, although if they find nothing wrong, it strengthens their case not yours. its not that difficult to tap in to any line, if u dont have the correct tools you could always bare back the wires and patch in that way. obviously if it has been done this way it will be random that your line was targeted. you could always slip the engineer a few quid if he finds nothing wrong, ask him to say it was crossed line or summit