I came across this page mentioning that Canadian citizens need to be accompanied by a guide when visiting, but then goes on to say it may not be necessary.
Iran visa for Americans, British and Canadians
Since February 2014, the rules for Americans have been extended to include British and Canadian passport holders. Canadians, British and Americans need to be accompanied be a guide while they are in Iran. [...]
It seems that at least for the embassy in Tblisi, Canadians do not need a guide anymore.
The problem is that Canada and Iran don't have diplomatic relations since 2012, so I can't have a reference from an Iranian mission in Canada about this, and I couldn't find anything on the Iranian MFA's website. The Canadian travel advisory doesn't mention that requirement, WikiVoyage mentions the requirement only for US citizens.
What's the official rule, do Canadians need an itinerary and guide when visiting Iran ?
Update: I was speaking to someone and it seems possible to get an independent visa if you know someone there that's prepared to sponsor it, even a regular citizen, in their case it was a friend. Would having a private sponsor satisfy that requirement and if so what are the formalities for that ?