First of all... you will NOT get any money for reporting an illegal alien. Second, you cannot be anonymous... this is not the crime hotline where you report criminals. And no, I don't think illegal aliens are criminals. I prefer an illegal mexican lady to be my nanny and not a rapist pedophile who killed 3 kids... so there IS a difference you know?
Third, reporting your illegal coworkers will affect not only them, but also your company, its owners, probably your boss and ultimately the hand that is feeding you and putting food on your table.
Last, think about it... if your issue is the fact that they are illegal and working at the same level as you are and you have all that BS in your head where you think you're being robbed or not promoted because a foreign national was smarter than you and went to college and speak more than one language, then by all means report them!... but start by talking to your boss, your HR department, and if nobody hears you... then call immigration and be ready to change jobs.
Now, if your problem with them is for whatever other reason that has NOTHING to do with their immigration status, then be a man and solve it by talking directly to them using your brains and your manners... if any is available.
Either way, good luck!
By the way... the IRS form is for fraud filing taxes... which doesn't mean they committed fraud by hiring illegals if they had faked social security numbers from their employees, so forget about that 10% which has nothing to do with illegals. The $1,000 fine is charged to the company as a penalty and not given to you. Whatever way you try to find to make money out of this will not work... otherwise somebody else would be cashing from 12 million people in this country.