Did they follow the greens to line up on EP instead of 20C perhaps?
Looks like my initial hunch was correct:
Incident: JAL B763 at Singapore on Jul 12th 2015, rejected takeoff from taxiway
By Simon Hradecky, created Wednesday, Jul 29th 2015 11:15Z, last updated Wednesday, Jul 29th 2015 11:15Z
A JAL Japan Airlines Boeing 767-300, registration JA606J performing flight JL-38 from Singapore (Singapore) to Tokyo Haneda (Japan) with 198 passengers and 10 crew, had taxied from the gate to depart runway 20C via taxiway WA (parallel to runway 20R), NC2 (North Cross 2) and was turning onto taxiway EP parallel to runway 20L [and parallel to 20C which it is next to, 20L is over on the military side - Airbubba] at about 02:25L (18:25Z Jul 11th) when the crew received takeoff clearance for runway 20C. Tower controller noticed the aircraft was accelerating for takeoff on taxiway EP reaching about 25 knots over ground, instructed the crew to stop and taxi onto runway 20C. The aircraft departed runway 20C about 6 minutes later and reached Tokyo Haneda with a total delay of 20 minutes.
A nice spaghetti bowl taxi diagram in the original article here:
Incident: JAL B763 at Singapore on Jul 12th 2015, rejected takeoff from taxiway
An eerie resemblance (but with a better outcome) to Singapore 006 in Taipei - big jet, creeping along in the dark, makes a right turn, gets take-off clearance - and the crew thinks they're on the runway.
Another similar incident, with nobody hurt, was Dynasty at ANC. They were cleared to takeoff on the customary runway 32 (now runway 33) at Kilo and they took off on taxiway Kilo instead:
http://www.pprune.org/rumours-news/1...-take-off.html