One of the news stories I read said a mobile cell tower was brought in. Those are a little more complicated than a repeater, I don't think the required equipment could by carried on a small airplane or helicopter.
As far as a scanner, you only get a very short burst of data from the cell phone, the ping at regular intervals so the scanner has to hit the right frequency at the right time to catch one. Then you would need multiple to triangulate a position. So while its technically possible, its not easy to coordinate.
Then you would have to hope they haven't ran the cell phone dead trying to make a call. Something I added to out vehicles is an 12v socket connected to clips which can clip on the vehicle battery should the rest of the electrical system die, that way I could still charge a cell phone if needed. This was after buying a new vehicle and finding out the quality of Japanese electrical systems when the whole thing burned up driving on a trip so we couldn't even power up the old car phone (back when they were installed in a vehicle and didn't have their own power source).