As she accelerated, the bus moved over the line, then stalled. As she struggled to start the vehicle the bells sounded, lights flashed and the railway barrier arms came down on top of the bus.
The woman fled the vehicle and ran down the railway line, waving her arms in the air to stop the oncoming train, which had just picked up morning passengers from Onehunga Railway Station, about 700m away.
The train driver, en route to Britomart in downtown Auckland, stopped.
Two other bus drivers coming out of the depot got out of their vehicles and managed to restart the bus.
A meeting between the woman and her bosses later resulted in her suspension on full pay.
In a letter seen by the Herald, the depot operations manager, Duncan McGrory, told her the company was conducting "an investigation into the allegation you positioned your bus across the railway lines".
"These allegations are potentially serious misconduct and an outcome may include the termination of your employment.
"The company believes that it would be in your best interests that you do not attend work while we are investigating these issues to ensure that a fair and unimpeded investigation is conducted."
NZ Bus chief operating officer Shane McMahon released a brief statement on Wednesday saying the incident was being investigated.
But after a meeting between the company, driver and union yesterday, she was taken off suspension and praised verbally.
Union branch secretary Gary Froggatt said he was working with the company over the way it had handled the incident and had advised it to update its ageing buses.