[Moto X General] glarepate:
I am running the adb and fastboot from the Android SDK. For the situations where that fastboot didn't work I used moto-fastboot built from their source code in the zip file called fastbootNfriends.zip. Of course you have to have a compiler and a version of 'make' to use the source code, so ...

Here it is: https://dl.dropboxusercontent.com/u/73634682/fastbootNfriends.zip

And of course there is a chain of trust/custody issue here too. I used it and had the results I documented previously, i.e., works good but sometimes needs to be run with superuser credentials.

I dug around over on the Moto X G+ Community site -- https://plus.google.com/communities/116517178872973348174 -- and found a link to the Developer SBFs at Motorola. I had to request a download from Moto but they gave me access in about 3.44 minutes. ;)

I dug their fastboot.exe out of the zip file (named VZW_XT1060_4.4.2-KXA20.16-1.25.2_1FF.xml.zip) and the link to that is here:

https://dl.dropboxusercontent.com/u/73634682/fastboot.exe

There was also a .dll file in the same [Windows] directory in the archive. It appears to be for use with ADB. I'm adding a link to it just in case the Moto fastboot.exe needs it to do something. If it doesn't need it you'll never know. If it does need it it will complain and you will have to get a copy of it. Maybe this will save a step. ;)

https://dl.dropboxusercontent.com/u/73634682/AdbWinApi.dll

And here is a copy of the .xml file that you would use to guide RSD Lite to flash the Verizon KK onto a Verizon phone. I am only including it for reference since it looks to use a slightly different procedure from the one for our phone -- not because I think it will be useful.

<?xml version="1.0"?>

<flashing>

<header>

<phone_model model="VZW_XT1060_1FF" />

<software_version version="ghost_verizon-user 4.4.2 KXA20.16-1.25.2 2 release-keysMSM8960PRO_BP_2323.031.111.00R" />

<interfaces>

<interface name="AP" />

</interfaces>

</header>

<steps interface="AP">

<step operation="flash" partition="partition" filename="gpt.bin" MD5="DA86065451752C9FAA4EE3AE41E91EE5" />

<step operation="flash" partition="motoboot" filename="motoboot.img" MD5="32232CAE7CA8459BD52FB9FC9A0E57F6" />

<step operation="reboot">

<step operation="flash" partition="logo" filename="logo.bin" MD5="5C8C2A8BA7F9E6F77DF5BEC5481A31A9" />

<step operation="flash" partition="boot" filename="boot.img" MD5="B813274A74FF1278A41C19905E76768B" />

<step operation="flash" partition="recovery" filename="recovery.img" MD5="9A3EA0D90080200826EE7B50164012BF" />

<step operation="flash" partition="system" filename="system.img" MD5="CC3A59472E7A577759A7CCF617B74581" />

<step operation="flash" partition="modem" filename="NON-HLOS.bin" MD5="1D4283E8D3B0EF528F2E4A1F67D9E04B" />

<step operation="erase" partition="modemst1" />

<step operation="erase" partition="modemst2" />

<step operation="flash" partition="fsg" filename="fsg.mbn" MD5="EC92255E54062C65AE72A4926361429B" />

<step operation="erase" partition="cache" />

</steps>

</flashing>

And you may be onto something with the adbd unsecure because I had to run fastboot and mfastboot as superuser in order for them to work correctly. Just the same since nothing we have seen so far recommends it or even mentions it in connection with what we have done so far it seems like something to try as an alternative if the standard method continues to fail for you.

"This message will self-destruct in 5 seconds and we will disavow all knowledge of you and your team, etc., etc., etc." No, actually, good luck. Let us know how it turns out!