The official HTC site HTCdev - Unlock Bootloader
give you a tool that is able to unlock All HTC Android devices launched after September 2011.
Unfortunately we are not in the list of the supported devices.
There is also a new tool ACS HTC Super Tool v2
, [UTIL][WIN][12/07] ACS HTC Super Tool v2 - xda-developers
. I need to give it a try, may be it will work for us.