TCU usually does not operate as BT unit... the ULF is BT unit, that can take upto 4 devices, the last paired device takes precedence in pairing to the ULF if two phones are within range... if you pair phone #5 to ULF, the phone #1 falls off the pairing...

ULF - ultra low frequency
TCU - telematic control unit

both connect to same harness, in old models, it is one or the other, in newer models - one device, two functions (also newer devices did SES, voice recognition)