Wikki has updated information that says:
""Costa Concordia is 290.20 metres (952 ft 1 in) long, with a beam of 35.50 metres (116 ft 6 in) and a draught of 8.20 metres (26 ft 11 in). She is equipped with a diesel-electric propulsion with six 12-cylinder Wärtsilä 12V46C[14] four-stroke medium-speed diesel generating sets with a combined output of 75,600 kilowatts (101,400 hp) and two 21 MW electric motors connected to fixed-pitch propellers.[15] Her service speed is 19.6 knots (36.3 km/h; 22.6 mph),[9] but during sea trials she could achieve a speed of 23 knots (43 km/h; 26 mph)"".

Costa Concordia

I asked a navy engineer about what type of power would be needed to operate a rudderless electronic prop steering system,that I understand most cruise ships have. He said "alot of power"
That's why I suspect (though cant seem to confirm) that a back-up generator, to give more power, may have been built into the upper decks. If power was not available for steering, oit would likely mean the delivery system to the props were down, and possibly damaged.

However, I recall the comments of a retired cruise ship captain on the CBC Fifth Estate. He said that cruise ship owners only install the safety equipment that they are required to install. He said something like" if they did not have to put in lifeboats, and had a choice to replace them with balconies that would bring in more money, they would likely do it"