Here we go :
1. First you need to root your phone, here's how.
2. Change you CID using the same method than for the One S.
Personnaly, I changed it to "HTC__203", which is the CID unbranded HTC phones have in France (HTC-FRA).
For example, "HTC__001" is HTC-WWE, which stands for World Wide English.
You can change it to whatever CID you like : choose it well. I can only recommend to use HTC__203 since it's the only one I tried and that it worked, but do as you please !
3. Flash stock recovery back. You'll find it here or here. Flash it like you flashed CWM recovery (into fastboot, using fastboot flash recovery xxxxxx.img).
4. Relock your bootloader. It's possible that it's not necessary, but it can't hurt ("fastboot oem lock", when in fastboot usb)
5. Run a RUU that matches you unbranded CID to get an "unbranded" rom.
You'll find them here, for example. The "RUU_K2_UL_ICS_40_HTC_Europe_1.17.401.5_R....e xe" one will work with HTC__203 and HTC__001 CIDs.
6. Go ask your phone if he can find any updates
WARNING : for the moment there's no way to change CID if you upgrade to JB since the newer HBOOT (v2.00) don't let you do it. That means that for now you won't be able to S-OFF if you upgrate to JB using this method. For now...