The daughterboard remains, but there is still a mystery left unsolved.
No phone operates without antennas, and antennas don't transmit signals well through metal walls. Considering that this daughterboard is on the receiving end of the motherboard's antenna cables and sits directly under the plastic bezel at the top of the phone, we're thinking it has something to do with wireless signals.
See those three spring contacts along the top of the board? They meet the rear case in an area obscured by the plastic bezel. If we had to guess, that's where HTC put the antennas.