I've entered the lounge on a Y ticket + TCGM card last Summer. As far as lounge access goes, silver or gold doesn't seem to make any difference in my experience (travel a lot with a silver member - who never needs to come as my "guest"). The lady manning the NRT transit desk gave me a voucher for entry - I've forgotten the name of the place. Small(ish) and rather crowded generic "airport" lounge. Nice staff (v. polite, as is usual in JP), the usual drinks, view of the apron and nicer than the main airport departure area - nothing worth holding your breath for though. Ask for a voucher at check-in.
Rgds