Bosland,
Try not to get too wrapped up in the distinctions you are trying to make as in this case I do not believe they were applicable.
The "Civilians" you keep referring to were anything but, they were members of the security services and were flying in direct support of the Operation that was NI at that time. As such they would have had the same "standing" as regular troops, this practice continues today and you would be amazed at the amount of "civilians" being flown on a day to day basis in current areas of op's so I believe you are heading up a dead end with that one.
As regards the 140 Kt notion it has already been explained quite eloquently that vibration in the Chinook above 140 Kts was something to behold and, whilst I have no first hand knowledge of authorising I doubt the weather minima for flights above this speed would have been a factor that was considered.