The game may not say that the combat re-assignment i's not temporary, but it doesn't say that it is permanent either. You know what they say about assuming. If you choose to perceive it as permanent, well that's up to you.
Sending Intelligence agents in combat situations isn't a death sentence nor is it unheard of, all major Intelligence agencies have paramilitary units that operate in wartime conditions and NOCs and other field agents aren't exactly sitting in cushy offices, eating ice cream and playing hopscotch.
Well this was not about Imperial Intelligence having combat trained section (like special forces). I am sure it had this kind of section anyway. This was about drafting agents, spies and techs into front-line infantry. Most of them were trained in intelligence gathering and espionage and not in infantry combat nor had any combat experience.
It is not necessary for the game to specifically state whether it was a temporary or permanent assignment. The common sense tells you that sending (mostly) combat-inexperienced personnel into front-line infantry units means they didn't really value their actual expertise or expected to have any use them in the future. Lack of combat training and experience, front-line infantry assignment and heavy casualties in battle of Corellia would completely decimate the ex-intelligence personnel (and statistically it was a "death sentence" for majority).