Your friend could just go and ask. The agents at the Worldclub in BOS are really nice, and the worst scenario is that they say, Sorry, sir. But I don't believe that C (business class) on AF - a three class airline - is equivalent to a WBC ticket, nor Business First on CO, nor yet BizElite on Delta, all of which are two class airlines...

[rant] It's my understanding that AF is responsible for a lot of the unpleasant inconsistencies in how status-holding members of various Skyteam airlines are treated, especially in the realm of lounge access. Apparently AF were so disdainful of BizElite compared to their wonderful First Class, that they refused any reciprocal lounge agreements based on fare class. [/rant]

Anyway, the BOS Worldclub does indeed have champagne (and better champagne than Delta serves in its BizElite lounges), and some extra snacks, during the departure period for the Virgin flight. I've only been in that club a few times during the right hours, but it was the case each time.