The idea for now is that they have their own public channels for that. They can use the private ones they know of if they want to route for LN->onchain swaps. Or they could pick a neighbor to wrap an LN invoice of theirs for a onchain->LN swap, the swap requester then pays to the other nodes pubkey and the emitter receives it through the private channel they share, shifting the balance from the original CJ change. There are many things to keep in mind though, but let's see how it unfolds.