Wendy Whitworth

Hello, I am hoping that someone can help me. We have a Concept 6 house alarm that we inherited. About 8 years ago we went on holiday and it went off and the neighbours couldn’t get hold of us for the code so they called an engineer to come and stop it. He told them that he would have to disarm it and it would never work again. It no longer has lights on the control pad and it has not been triggered during the last 8 years even when the power has gone down. I recently had an electrician in and I asked him if he could remove the old motion sensor from the living room as it has broken and is dangling down. He said he didn’t want to touch it as even though the alarm was disarmed, cutting the wire may still trigger it. Is this true or am I safe to just cut the wire? Thanks