A foiled plot to derail a Via Rail train last year has served as a wake-up call to Canada's largest regional transit company that the country's mass transit systems are a vulnerable target for attacks, CBC's The National reports.

GO Transit moves up to 300,000 people everyday, and is turning to the RCMP terror investigator Sgt. Derek Macdonald to learn how to operate with increased vigilance to spot suspicious behaviour and terrorist weak spots. 

GO Transit terror school

RCMP's training course teaches companies to spot their own security gaps. (CBC News )

The plan to derail a passenger train in the New York-Toronto corridor was a homegrown scheme by two men allegedly backed by al-Qaeda, and it was a game changer for GO Transit.

Macdonald runs a training program for security workers, and has already helped Toronto landmarks like Union Station and the Air Canada Centre operate in a new state of heightened awareness. 

He is in big demand and his lesson for his newest GO Transit students is deceptively simple. 

'Think like a cop, think like a terrorist'

"I'm actually asking them to think like a cop -- and to think like a terrorist," Macdonald said. "The day you take a second off could be the day an attack is taking place." His training sessions involve exercises in which students have to plan their own terrorist attack. 

GO Transit

GO Transit is the largest regional transit company in Canada, moving nearly 300,000 people a day. (CBC News)

Students plan everything from how to recruit members, to how to get their hands on explosives to avoiding detection.

When viewed from a different lens, subtle activities on public transit can reveal something a lot more sinister, he says. Thinking like a terrorist will hopefully help security workers spot them more easily.