Turn based mode is not disabled. I just used it with a team earlier today to clear the Arcane Cannons from the Tower. There must be a problem with your save. It can bug out in certain circumstances. Like if you hit the space bar too many times when there is a lot going on will break it.
I have tested this numerous times. I even found a walkthrough online that points out how you'll be kicked out of turn-based mode if you enter with it on. And it is ONLY for that segment. I can turn on turn-based mode immediately before and immediately after I save the councilor. It seems very unlikely its a bug; can you tell me which version you're using?
