It's been a few months, but for at least a few years the PY bubbles were consistently mini bottles of Champagne Vollereaux. Nothing to write home about, but perfectly inoffensive IMO esp for PY. (I even had it served to me in J once, presumably because I had personally—okay, probably not me alone—drank all the J champagne loaded.)

Meanwhile a certain TPAC JV partner of JL cannot even commit to serving Champagne in J on their flights...