This is another reason Apple needs to get away from Qualcomm
I have no idea if these scare stories about iPhones turning on and transcribing conversations are true. But Qualcomm controls the baseband software in the iPhone and every other phone using Qualcomm cellular IP, so they could make it do this and the phone's OS couldn't stop it (though I don't see how the phone's owner would know it is happening since it couldn't display anything on the screen)
Apple's plan with Intel is to eventually license the IP and include the cellular block on their SoC, rather than buying a chip from Intel. And they'd be able to write their own baseband software (or more likely modify Intel's software) and could insure that no built in telco/spook backdoors are present.