The ^ event prefix currently works
only on the following types of events: ACTION, BAN, CHAT, DEHELP, DEOP, DEVOICE, HELP, INVITE, JOIN, KICK, MODE, NICK, NOTICE, OP, OPEN, PART, PING, TEXT, UNBAN, USERMODE, VOICE, QUIT, SERV, SERVERMODE, SERVEROP, SNOTICE, TABCOMP, TOPIC, WALLOPS.
As you can see the PONG event is not supported with ^ prefix.
