I heard this from a customer so take this with a grain of salt but he told me he was an Android Developer and had heard of an interesting "trick" concerning all HTC Android phones.
These phones apparently have a SECONDARY bootloader that is completely hidden and disabled by default and that all those phones are HARDCODED to immediately enter into it the moment they get connected to a specific USB cable.
The guy was looking for the cheapest possible, well, item really, to buy and then proceed to cannibalize as a test to its' validity (he bought an old Motorola handsfree) so it seems he wasn't sure of it either.
Apparently what needs to be done is that the PLUG needs to be completely stripped and either two resistors or two capacitors (I forget which) of specific values need to be soldered to two specific lungs of the plug.
I am sorry I am being this vague but that was all the information I got from him in the matter of the couple of minutes it took him to buy the handsfree.
Perhaps there's sth to be looked into by some people better equipped than I?
EDIT: On second thought, it makes more sense if what he said was to solder A resistor/capacitor to TWO specific lugs of the plug, perhaps?
I kinda remember him saying that the plug itself doesn't even really need to lead to anywhere but it's more like the means to connecting the resistor/capacitor to those two lugs...
He also said that that's how HTC themselves un-brick bricked phones. He didn't appear to be talking just for Dev phones either.
I am sorry I really do not know any details.