My workplace has put it out firmly, not to communicate with immigration authorities unless they have a warrant signed by an actual judge, those are the only things that give them any pretense to operate. They will try to use a warrant signed by ICE themselves, or otherwise bamboozle their way inside your workplace, once theyre in they have total discretion and can make up any pretense after the fact to do as much snooping as they want. Dont give them any opportunity you dont have to and play stupid if possible.