The arrests in Montreal and Toronto bolstered allegations by some governments and experts of a relationship of convenience between Iran and al-Qaida.
Bruce Riedel, a CIA veteran who is now a Brookings Institution senior fellow, said al-Qaida has had a clandestine presence in Iran since at least 2001 and that neither the terror group nor Tehran speak openly about it.
"The Iranian regime kept some of these elements under house arrest," he said in an email to The Associated Press. "Some probably operate covertly. AQ members often transit Iran traveling between hideouts in Pakistan and Iraq."
U.S. intelligence officials have long tracked limited al-Qaida activity inside Iran. Remnants of al-Qaida's so-called management council are still there, though they are usually kept under virtual house arrest by an Iranian regime suspicious of the Sunni-/Salafi-based militant movement. There are also a small number of financiers and facilitators who help move money, and sometimes weapons and people throughout the region from their base in Iran.
Last fall, the Obama administration offered up to $12 million in rewards for information leading to the capture of two al-Qaida leaders based in Iran. The U.S. State Department described them as key facilitators in sending extremists to Iraq and Afghanistan. The U.S. Treasury Department also announced financial penalties against one of the men.
The investigation surrounding the planned attack was part of a cross-border operation involving Canadian law enforcement agencies, the FBI and the U.S. Department of Homeland Security.
The attack "was definitely in the planning stage but not imminent," RCMP chief superintendent Jennifer Strachan said Monday. "We are alleging that these two individuals took steps and conducted activities to initiate a terrorist attack. They watched trains and railways."