SE nominee is non-altitude member; upgrade windown latitude fares
 

The first question is: if a non-altitude member is a SE nominee - and such customer buys a latitude or flexible PE fare, what is the temporal window for that customer to upgrade - at time of booking, or within 7 days of flight departure?

If a non-altitude or altitude customer buys a PE (lowest) economy fare, and at least one segment is in a 2 cabin plane, presumably that person will get an economy seat. What is the upgrade window for the non-altitude or altitude member? Someone told me that a PE (non-flexible/lowest) economy fare ticket is counted like a latitude fare on a 2 cabin plane

Why not just check the calculator that's online? There's an option for "None" under Air Canada Altitude status.

Good Idea - it stated 7 days for the answer to the first question.
But one can argue that the calculator does not resolve one question:

does the question about the altitude status of the member refer to that of the person requesting the upgrade (which is what my friend is stating) or of the passenger who is flying and for whom the upgrade is being requested (that is my position).

The calculator would no be able to answer the second question.

The upgrade window for FLEX was SE(and not the nominee threshold). Would suspect Latitude would work the same way?

You can always book and cancel on 24 hour if it doesn't work out, latitude should be anytime upgrade confirmation.

But then the 7 day window - which is associated with a non-altitude member - for latitude fares - for whom does it work?

I can think of two ways to have eUps but no status. It's uncommon, but possible.

As was mentioned, the windows/co-pays/etc. are determined by the status of the person requesting the upgrade.