Did ICE constantly make those plans only to have them stomped down by Obama's political appointees? Or did they just start to get serious on 11/9?
Even if they can't catch them all, they can get the illegals scared and constantly on the move, which makes them unreliable employees and therefore less valuable to hire for anything other than day labor. If you want someone who can work in your kitchen tomorrow and next week you'll have to hire a citizen or legal immigrant. Winning!
The plan was, prior to the election, ICE would go out and make some arrests. These would be people who were no danger to US citizens, like females who had been here for 20 years and worked as maids.
They would make a court case out of it, and the illegal alien plaintiff would win the case. The government would back down, and the new President would officially revise the immigration laws to conform.
BUT, Hillary didn't win. It was all for naught, and now they have no choice but to actually deal with the problem. They can't just stop because Trump won. It would look like they weren't doing their job.
The old game was to selectively deport illegals based on bribery from corporations that use illegals. The new game is that the law is the law. Many don't like the new game, but that's tough.