Elite status on CO will not get you Pres Club entry, even at the plat level. Only way to get into the club is to buy a membership, have a pass, buy a BusinessFirst ticket or if you have a platinum AMEX or a Priority Pass club membership (with PP's fees).
Just wanted to correct this...you can get entry as a Plat to any SkyTeam lounge on the day of travel if traveling internationally on a SkyTeam airline. This perk got me into the KLM lounges in AMS (FWIW) when traveling in Y since Amex Plat is not accepted there.