yes actually. and it's fairly simple form an implementation perspective.
I can't really get into the specifics of the code as I haven't worked with rmxos in a while but basically it works off of virtual map ids.
In short every map in the game and thus every dungeon has a map id. RMXP has an inbuilt limit of 999 maps, that means map ids run from 1-999. there are a few ways to get more than 999 maps but that's besides the point. Basically you arbitrarily pick a point at which it would not be possible for a virtual id to collide with a real id. Ie it would be a bit ridicules to have over 10k maps so you say that all ID's over 10,000 are virtual and thus belong to an instanced map.
if a client is told to move to a map with say id 10,002 it knows that it's moving to an instance and needs to consult the server as to what map to load. The server of course needs to keep a record of what virtual ID's it has handed out to what players on what map. a simple request form the client to the server gets the client the real map id and it can load the map data.
The server would need to keep track of what map IDs are in use and dispose of and reuse them as needed.
this kind of system could even be used for player housing. permanently assign a virtual ID to a player for their house but load the same template house map. then add things bacsed on what they have placed in the house.
again I don't really have the time to make the system my self but it's actually really easy to do. if you want to make the attempt your self, I and most everyone else here would be happy to guide you through the process.