Can Port Control Protocol (PCP) work for two ISP customers that want to host a service on same port within CGN?

Let's say there are ISP customers that were assigned to a shared address space of CGN. connections were established and PCP client is enabled. Now what happens if two customers wanted to host a webserver on port 80? Can PCP establish that connection on two simultaneous identical hosts behind CGN? Or will it reserve the first port request to whoever customer requested the incoming connection first?