It's a headline-grabbing stunt.
In the nicest possible way, mind you. I don't doubt they genuinely want to see if they can do it, and one day deliver it, but what are the chances of them actually delivering a saleable, sustainable product in the next 5 years? What would the AUP or download limits, or peak time throttleing policies look like, for example? You would run over the current policies in a matter of seconds at that sort of speed, and applying wholly different policies to a gigabit service whilst retaining the current ones on other tiers would very quickly give the lie to any suggestion that somebody with a 'mere' 100Mb service could in any way be capable of congesting the network.