I was thinking if there was a platform staff etc on duty, the device would be turned off anyway. As the staff member would be able to keep an eye and would move any riff-raff or troublemakers on.
Also I am led to believe these devices only cause great annoyance after a certain period of time. A genuine traveller won't be around long enough (especially at Ealing BDY) to get annoyed by it... but the people hanging around for a long time, loitering, drinking, taking drugs etc etc.. would get the effect and 'move on'
Oh and for the record, I am in mid 20's and have worked on the railway since late teens!
But a 30 year old loitering would NOT be detered by it, where as a 16 year old waiting for the last train home after meeting with friends would be.