We don't have an official policy (controllers should use their best judgement in dealing with this), but here's a summary of the issues:
This will be a problem we have to deal with for quite some time (especially since Microsoft has discontinued development of MSFS, and the default scenery is frozen in time). In the RW, the old taxiways Q and S have been closed and demolished to permit construction of the new international terminal. Eventually taxiway S will reopen, but west of its old location. Taxiway R was constructed in the last year or so to provide a corridor (other than AA) between the N and S sides of the airport.
Obviously, the problem for the foreseeable future is that pilots will have a variety of sceneries and we have no consistent way to determine what's included in each scenery or what scenery a pilot is using. The only connector taxiway that will be unchanged is AA, which isn't terribly convenient, especially for departures during W ops. Luckily, we don't need to move departures from the N side to the S side very often.
For now, it's a safe bet that aircraft have scenery matching the sector file LAX layout, and I think it's reasonable for a controller to assume that the pilot has taxiways Q, S, and AA depicted. That will evolve over time, and it may become necessary to have some mechanism during events to know what is displayed to pilots. Maybe we'll ask pilots who have modified scenery (or X-Plane when its default scenery is updated), to make a note in the flight plan remarks.