You probably know that all digital sensors are sensitive to near-infrared and that most cameras block out infrared to avoid contaminating the colours. I found that my iPhone camera is indeed sensitive to IR and could clearly see the infrared emitters from a headphone loop system at a conference I recently attended.
I had wondered many years ago whether flooding a cinema screen with infrared could hamper anyone wanting to film the movie from the screen. Back in the days of poor filtering this may well have worked but I suspect filtering would remove the infrared with modern cameras.
Apple have applied for a patent for a mechanism that carries a code in an infrared signal 'broadcast' at a venue, decoding it in the phone (or other device) and using the result to determine whether the camera should be deactivated. This is a similar idea to the coding that prevents scanners and photocopiers from copying banknotes. The BBC carried a story reporting that rapper Tinie Tempah was against this idea because he likes his fans to video his concerts (a bit like the Grateful Dead for those of us a little older ... the Dead used to set aside an area in front of the stage for fans who wanted to record their concerts). Apple's system would be optional: it would be up the venue/performer to use it to disable cameras.
Some of the artists interviewed by the BBC had a simple view. They didn't mind being videoed but they thought their fans should actually be enjoying the concert instead.
Of course Apple could configure the iPhones to receive those headphone loops (usually helpful to people with impaired hearing). That would be nice: you could use your own headphones.