I did a teardown (more like ripapart) as well and then I found your article. The central chip they couldn't figure out has marking NRF CO 24LEDN which I think stands for custom version of NRF24LE1 for Disney ("DN") from Nordic Semiconductor. A quick look on Nordic Semiconductor site provides this information :
The nRF24LE1 integrates an nRF24L01+ 2.4GHz RF transceiver core, enhanced 16MHz 8-bit 8051 compatible CPU, 1kB + 256B RAM, 16kB embedded Flash, and a wide range of system peripherals including a hardware AES accelerator, 16MHz and 32kHz RC oscillators, ultra low power 32kHz crystal oscillator, 12-bit ADC and SPI, 2-wire and UART serial interfaces.
The nRF24LE1 is available in 3 package options ( the first one looks exactly like the chip in the band) - 4 x 4mm 24-pin QFN with 7 generic I/O pins
We made a reservation and were directed to order our food online for the "Beauty and the Beast" restaurant in the Magic Kingdom. When we arrived for our reservation, we were told to get our drinks and silverware and sit down anywhere we wanted in the three very large dining rooms, and our food would be brought to us. Within 15 minutes, our food arrived, and the waiter confirmed that the Magic Band was used to locate us.