Early Media, aka in-band information, is sent from the network to the calling phone in some circumstances, to provide alternative tones or extra information about the status of the call. In GSM this is available because of "Early Assignment" of the TCH. This early assignment is also possible in the called phone, but I have never heard/read of a use for it, besides the initial purpose of avoiding delays.
Now, question is, does assignment of the TCH implies the capability of receiving early media FROM the mic of the phone, before the actual start of the conversation? And if the capability exists, has it been used? Perhaps in outgoing calls there were plans to offer *44, voice activated dialing, services and then it is a sort of legacy.
Of course the worst possible case is the inbound call: TCH and microphone open in the called phone without actual ringing of the signal (call, abort with silent notification and leave channel open until the timer expires, then call again).