[HTC One S] ojomio:
Solved!

Read this thread http://xdaforums.com/showthread.php?t=2500424

RUU doesn't get zip-flashed with message in first post, but inside the FOTA there is a firmware.zip , which does. It does not contain ROM, though, but that's irrelevant as it will flash your hboot partition, and that even without S-Off

sudo ./fastboot flash zip ./firmware.zip
[sudo] password for crystal:
sending 'zip' (35551 KB)...
OKAY [ 2.749s]
writing 'zip'...
(bootloader) adopting the signature contained in this image...
(bootloader) signature checking...
(bootloader) zip header checking...
(bootloader) zip info parsing...
(bootloader) checking model ID...
(bootloader) checking custom ID...
(bootloader) checking main version...
(bootloader) checking hboot version...
(bootloader) start image[hboot] unzipping for pre-update check...
(bootloader) start image[hboot] flushing...
(bootloader) signature checking...
(bootloader) [RUU]WP,hboot,0
(bootloader) [RUU]WP,hboot,100
FAILED (remote: 90 hboot pre-update! please flush image again immediately)
finished. total time: 8.742s
crystal@crystal-X502CA:~/Android/adt-bundle-linux-x86_64-20140702/sdk/platform-tools$ sudo ./fastboot flash zip ./firmware.zip
< waiting for device >
sending 'zip' (35551 KB)...
OKAY [ 2.676s]
writing 'zip'...
(bootloader) adopting the signature contained in this image...
(bootloader) signature checking...
(bootloader) zip header checking...
(bootloader) zip info parsing...
(bootloader) checking model ID...
(bootloader) checking custom ID...
(bootloader) checking main version...
(bootloader) checking hboot version...
(bootloader) start image[adsp] unzipping & flushing...
(bootloader) [RUU]UZ,adsp,0
(bootloader) [RUU]UZ,adsp,12
(bootloader) [RUU]UZ,adsp,24
(bootloader) [RUU]UZ,adsp,36
(bootloader) [RUU]UZ,adsp,48
(bootloader) [RUU]UZ,adsp,61
(bootloader) [RUU]UZ,adsp,72
(bootloader) [RUU]UZ,adsp,84
(bootloader) [RUU]UZ,adsp,94
(bootloader) [RUU]UZ,adsp,100
(bootloader) [RUU]WP,adsp,0
(bootloader) [RUU]WP,adsp,100
(bootloader) ..... OK
(bootloader) start image[boot] unzipping & flushing...
(bootloader) [RUU]UZ,boot,0
(bootloader) [RUU]UZ,boot,10
(bootloader) [RUU]UZ,boot,21
(bootloader) [RUU]UZ,boot,34
(bootloader) [RUU]UZ,boot,46
(bootloader) [RUU]UZ,boot,57
(bootloader) [RUU]UZ,boot,67
(bootloader) [RUU]UZ,boot,80
(bootloader) [RUU]UZ,boot,95
(bootloader) [RUU]UZ,boot,100
(bootloader) [RUU]WP,boot,0
(bootloader) [RUU]WP,boot,99
(bootloader) [RUU]WP,boot,100
(bootloader) ..... OK
(bootloader) start image[cs] unzipping & flushing...
(bootloader) [RUU]UZ,cs,0
(bootloader) [RUU]UZ,cs,100
(bootloader) ..... BYPASSED
(bootloader) start image[cs] unzipping & flushing...
(bootloader) [RUU]UZ,cs,0
(bootloader) [RUU]UZ,cs,100
(bootloader) [RUU]WP,cs,0
(bootloader) ..... OK
(bootloader) start image[pg2fs_spcustom] unzipping & flushing...
(bootloader) [RUU]UZ,pg2fs_spcustom,0
(bootloader) [RUU]UZ,pg2fs_spcustom,99
(bootloader) [RUU]UZ,pg2fs_spcustom,100
(bootloader) ..... OK
(bootloader) start image[recovery] unzipping & flushing...
(bootloader) [RUU]UZ,recovery,0
(bootloader) [RUU]UZ,recovery,12
(bootloader) [RUU]UZ,recovery,22
(bootloader) [RUU]UZ,recovery,34
(bootloader) [RUU]UZ,recovery,45
(bootloader) [RUU]UZ,recovery,57
(bootloader) [RUU]UZ,recovery,68
(bootloader) [RUU]UZ,recovery,81
(bootloader) [RUU]UZ,recovery,91
(bootloader) [RUU]UZ,recovery,100
(bootloader) [RUU]WP,recovery,0
(bootloader) [RUU]WP,recovery,99
(bootloader) [RUU]WP,recovery,100
(bootloader) ..... OK
(bootloader) start image[rpm] unzipping & flushing...
(bootloader) [RUU]UZ,rpm,0
(bootloader) [RUU]UZ,rpm,100
(bootloader) signature checking...
(bootloader) ..... OK
(bootloader) start image[sbl1-1] unzipping & flushing...
(bootloader) [RUU]UZ,sbl1-1,0
(bootloader) [RUU]UZ,sbl1-1,100
(bootloader) signature checking...
(bootloader) verified fail
(bootloader) ..... BYPASSED
(bootloader) start image[sbl1-2] unzipping & flushing...
(bootloader) [RUU]UZ,sbl1-2,0
(bootloader) [RUU]UZ,sbl1-2,100
(bootloader) signature checking...
(bootloader) verified fail
(bootloader) ..... BYPASSED
(bootloader) start image[sbl1-3] unzipping & flushing...
(bootloader) [RUU]UZ,sbl1-3,0
(bootloader) [RUU]UZ,sbl1-3,100
(bootloader) signature checking...
(bootloader) ..... OK
(bootloader) start image[sbl2] unzipping & flushing...
(bootloader) [RUU]UZ,sbl2,0
(bootloader) [RUU]UZ,sbl2,100
(bootloader) signature checking...
(bootloader) ..... OK
(bootloader) start image[sbl3] unzipping & flushing...
(bootloader) [RUU]UZ,sbl3,0
(bootloader) [RUU]UZ,sbl3,100
(bootloader) signature checking...
(bootloader) ..... OK
(bootloader) start image[tz] unzipping & flushing...
(bootloader) [RUU]UZ,tz,0
(bootloader) [RUU]UZ,tz,100
(bootloader) signature checking...
(bootloader) ..... OK
(bootloader) start image[wcnss] unzipping & flushing...
(bootloader) [RUU]UZ,wcnss,0
(bootloader) [RUU]UZ,wcnss,20
(bootloader) [RUU]UZ,wcnss,100
(bootloader) [RUU]WP,wcnss,0
(bootloader) [RUU]WP,wcnss,100
(bootloader) ..... OK
(bootloader) start image[radio] unzipping & flushing...
(bootloader) [RUU]UZ,radio,0
(bootloader) [RUU]UZ,radio,6
(bootloader) [RUU]UZ,radio,11
(bootloader) [RUU]UZ,radio,18
(bootloader) [RUU]UZ,radio,23
(bootloader) [RUU]UZ,radio,29
(bootloader) [RUU]UZ,radio,35
(bootloader) [RUU]UZ,radio,41
(bootloader) [RUU]UZ,radio,47
(bootloader) [RUU]UZ,radio,53
(bootloader) [RUU]UZ,radio,59
(bootloader) [RUU]UZ,radio,65
(bootloader) [RUU]UZ,radio,71
(bootloader) [RUU]UZ,radio,77
(bootloader) [RUU]UZ,radio,84
(bootloader) [RUU]UZ,radio,89
(bootloader) [RUU]UZ,radio,95
(bootloader) [RUU]UZ,radio,100
(bootloader) [RUU]WP,radio,0
(bootloader) [RUU]WP,radio,47
(bootloader) [RUU]WP,radio,95
(bootloader) [RUU]WP,radio,100
(bootloader) ..... OK
(bootloader) start image[rcdata] unzipping & flushing...
(bootloader) [RUU]UZ,rcdata,0
(bootloader) [RUU]WP,rcdata,0
(bootloader) ..... OK
OKAY [ 53.318s]
finished. total time: 55.994s

Don't forget to relock before flashing the OTA's firmware

Otherwise it will report "99 Unknown Error"