The Trudeau campaign promised to improve diplomatic relations with Iran, which had been cut by the Harper government, at least in part, because of security concerns in Tehran. However, as this al Monitor article argues (please excuse the shameless self-promotion), the issue does not appear to be high on the agenda for either country.
“Pointing to the fact that Tehran is not a key trade, investment or security partner for Ottawa, James Devine, assistant professor of politics and international relations at Mount Allison University, told Al-Monitor, “On the Iranian side, there is less need for better relations with Canada. Tehran had previously seen Canada as a gateway to better relations with the West. However, since the July 14 Joint Comprehensive Plan of Action [JCPOA] was signed, relations between Iran and the Europeans have improved significantly. I don’t think Canada is as important to Tehran as it once was.” Adnan Tabatabai, a Berlin-based Iranian political analyst told Al-Monitor, “Iran-Canada relations have not been essential for either side. It is rather the presence of Iranians traveling back and forth to Canada that connects these two countries.”
Links to further reading on the Harper government’s policies can be found below. The first provides the details of how Canada managed the closure. The move, which was announced by the PM while he was visiting Moscow smacked of grandstanding at the time. This CBC report confirms that impression arguing that the Canadian delegation left Iran quickly and quietly because as Canada’s Foreign Minister himself admitted “frankly, we didn’t want them to discover what our actions would be and then try to expel us before we could expel them.”
Inside Canada’s top-secret diplomatic exit from Iran
CBC News gets an inside peek at how Canadian diplomats got out — and left little behind
http://www.cbc.ca/news/politics/inside-canada-s-top-secret-diplomatic-exit-from-iran-1.1367496
The second link suggests the threats sighted as a cause for leaving Iran were exaggerated.
Iran embassy report suggests little threat months before closure
IR Theory & Practice 