Here's my take on this:
Sounds like a good idea, but this is what I think (know) will happen:
You witness an employer hiring an illegal so you call;
ring ring
"ICE"
"Yes, I would like to report Mom and Pops Lawn Service for hiring illegal aliens"
"OK sir, thank you very much"
(insert sound of crickets churping)
If you see by my reports, I am calling businesses I patronize and asking for a guarantee that they do not hire illegal aliens. That may do more good. If enough people complain, however, about some local business, it should worth a story in the newspaper. The business will not want that to happen.
(insert sound of crickets churping)
And......(insert sounds of loud snoring)