@jonny522 - The forum post you are linking to was for TS4. While TS3 was mentioned to provide a comparison, I didn't see where actual travel in TS3, which means to and from entire worlds that are different from the one being actively played, was discussed.
In TS3, the NRaas Traveler mod opens up a lot of travel and vacation world related possibilities. But even with that one in play, it is not possible to push sims from the currently being played world into another one. The best you would be able to do even with Traveler is to travel these sims yourself to a foreign world, any world that you have installed, invoke the mod's Change Hometown procedure on them, then leave them there in their new homeworld and transition active play back to the original one. That's quite a bit more than sending them away just "for a while" as they would become official residents of their new world and this may be more than you were hoping to go through in order to arrange such a scenario.
