Small Transport; Low Wing; 2 Turbojet Eng
Communication Breakdown; Other / Unknown
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors
We were holding short of Runway 06L at CYYZ and takeoffs and landings were being conducted on the runway.  Captain had mentioned he had a commute to catch upon arrival and we were issued a wheels up time.  At the wheels up time; the aircraft ahead in the run up area was cleared for takeoff.  I glanced right and saw the next arrival for the runway and mentally thought we might be able to get out before him if we get clearance right now.  The Captain released the parking brake to inch forward to the hold short line since the aircraft ahead had departed.  As we were rolling; the Tower Controller issued instructions; 'Call sign ABCD; amend SID instructions; stop climb at 3;000; airborne turn right heading 1-0-0 degrees.'  As the instruction was received; I read it back and then focused my attention on the automation to reset for the new departure instructions.  Due to the lack of familiarity with the new departure profiles; I had to pause for a few seconds to think of how the automation should be configured.  I then input the correct automation for the new departure instructions.  As I looked back up outside the aircraft; I saw that we were lining up onto the runway.  As my mental focus had been inside the airplane; I did not immediately perceive any error.  I then began to try and think back into my short term memory whether we had been cleared to line up.  As we lined up fully; ATC instructed another aircraft to go-around.  It then clicked in my brain that we had never been cleared to line up and wait and I verbally said so.  The Captain then also realized his error.  We departed uneventfully afterwards.     Some factors in my mind at the time included how ATC worded the SID amendment in a way that sounded like the precursor to a line up and wait or takeoff clearance. Another was the glancing of the next arrival.  Since our wheels up time had come; my mindset had indicated that we were next and had enough room if we got clearance to takeoff right away.  When ATC issued the SID amendment; the aircraft was already rolling forward as my head went down.  I felt aircraft movement because we had been creeping forward but did not realize how far we had gone before putting my head back up.  Threats; lack of runway status lights; no ATC intervention prior to incursion leads me to believe CYYZ does not have ASD-X that would have sent an automated alert; a very rushed method of new takeoff profiles introduced; and a single runway for takeoffs and landings when a parallel runway was nearby.  Errors- looking down and focusing on automation rather than on surface movement and not realizing we had crossed hold short line without clearance.
Air carrier First Officer describes the events leading up to a runway incursion at CYYZ; requiring an aircraft to go-around.