It is definitely possible to do fan simulations in OF, in three different ways:
The first of those options is actually available in BF as we speak, through the custom boundary condition object. It would be very educational for you to try and set up a case in this fashion. You can find tutorials for both of these boundary conditions in the OF tutorial folders (just search the keywords).
The MRF option is not yet easily available through BF, although not impossible to set up. It is still a vanilla steady-state simulation, with the same models, but has an additional implication during meshing (creating cellzones) and running (using fvOptions). It will be something we plan to add in BF in the future.
The transient case is the hardest and probably the last one to be attempted.
The one issue I found with RBM (and MRF) inside OF was that snappyHexMesh would cause a few problems while meshing the cases, since there are very specific requirements for the rotating regions. I would routinely resolve these with another mesher (cfMesh), I will need to revisit soon and see if this still stands now.
Hope this helps.