Realmbots Event Notifier worked by the bots in the real, They got the message from Oryx and sent it to the Realmbot servers to send out to players w/ in a fraction of seconds. Calling a horse out via. a notifier is probably alot more difficult unless the players them self call out the dugeons and even then, There are WAY to many troll and hopping servers to TP to the caller would be a pain as they tend to leave w/ in 5 seconds of calling (The same amount time it would take for the notifier to recieve info and pass it on to you.)
TL;DR: Probably but a pain in the ass to work with.