Seems like they could have one of those mini femtocells that cellphone companies will send you if you have no reception at your place - these just plug into your home internet and then rebroadcast a 3G or 4G signal. I still have an older 3G one from Sprint I am keeping around (probably wont even work anymore).
One of these could temporarily be plugged in on request - they could have just a few of them (at whoever is head of IT) for different carriers just for this situation.