I just tried to have two pirates enter Joey Karo's Lair in Flotsam, but they were sent to different dungeons. I tried to port to the other pirate and got this message: "You cannot port to that pirate at this time." I don't think this is the message you get if the pirate has ports turned off, and I verified that Friend Teleports said ALLOW.
I even restarted my computer and re-logged into both accounts, but it is still happening. This dungeon is on the main questline and has a sigil, so it should not be solo-only.