You can either cheese it by going down to Arcade and still be careful, move slow, sync your teammates to the 3 sniper toward for when the scripted part of the lazy-esque mission starts, drop the snipers and get on your favorite LMG (2 if at all possible), you will have more chances of not dying and park a helo nearby but far away that it doesn't get blown up, call guns for hire, throw a rebel diversion nearby and be done with it. That is what I have learn how to do so, more so when you are doing the challenges.

Now, if you don't want to do the mission at all (I never did until I learn the cheese version of it) and if I remember correctly, the work-around is that when you spawn, you immediatly Un-Tag the mission and tag some other mission right away? and I beleive that will set it off.

If that is not the case, one of the 2 or 3 regulars here will chime in with the correct answer but you are going to have to wait because there is only a handful of us still here.