oh man, then you'd have everyone pouring into one arena using the squad loophole, it'd be totally rediculous.
HT deliberately put in a command for this, you can send a PM to anyone in all arenas by typing '.p [gameid] [message]'
go to an arena, use the .sr command to find your guys, and if you cant get to them, then ask them to come and join you in another arena. if they don't want to then they're being right arses and you're in the wrong squad. simple as that mate.