I was looking at fares from YYZ -> EDI (via LHR). There's a flight that features the new interior with pods in Business Class.

When I click on that flight using lowest cost business class fare (C) the website tells me that there's no business class available for the YYZ / LHR leg and that "you will be seated in economy class". When I select the full J fare, magically there are seats available in business class.

I've never come across this before, so I was wondering if I took the C class ticket, would I be able to "upgrade" myself using a certificate? Certs of course state Y, M, U fares only for upgrades, so would they work for C?

Just wondering. I'll probably book the full J fare anyway but I was curious to see how C fares really work.