If you are in BE either with cash, miles, or SWU then that gives access to the skyclubs. If you're holding a ticket that shows J/C/D/J then that is business class. Upgrading with miles or SWU to Z entitles you to full privileges. Yes the original booking is listed on the ticket, but it also shows something like "SWU" next to the fare code to show the upgrade was paid for.

If you are given an op-up at the gate then no I don't think so.