With worlds already in play (as opposed to during their CAW design stage) and do you mean without loading the source neighborhood or without loading the destination one?
If both worlds exist and are connected within the same game save (NRaas Traveler), you can do this as a pull from the destination world using MasterController's Add Sim filtered to Homeworld.
I've often wished for a way to push sims into other worlds rather than traveling them there or having to go there and pull them in, but I don't think this is feasible to arrange. They wouldn't have any way to be housed in the not actively being played destination world, so I imagine they would kind of get stuck in limbo as part of the homeless NPC population if such were even made possible.