I arrived in T1 last week and there is a TIM store airside right before you take the escalator down to the baggage claim area. You can buy a TIM for visitors for 30 euro using your credit card on their web site. It gives you a print out with a confirmation code. Just give the print out to the clerk along with your passport, and they will set you up with a sim card that gives 4GB of data and 100 minutes of voice. There was no line when I went, but it still took the person about 10 minutes to handle my setup. So if there is a line, plan on 10 minutes per person. The sim card worked in Amsterdam as well.