I find it difficult to believe this. What you have posted is a link to a web site that provides devices for 'auditory assistance'. The range on the transmitter that I looked at was a mere 1000 ft. That's barely out into the auditorium - where the folks don't need this device. What you may be referring to - might be for the hard-of-hearing - or deaf section of the auditorium.
Yes, a bit of a mix-up here. This announcement applied to Assemlies at Assemly Halls (and local kingdom halls). I'm actually not to sure what they do for the large conventions in public buildings.