Yes, it is possible to use the map control offline.
You can use it with the EmptyProvider which allows using RadMap without connection to any real imagery services (Virtual Earth, OpenStreetMaps etc). Usually it is used to show geospatial data from shape-files or from KML. For more information please take a look at the following help topic:
You can also use the UriImageProvider which allows you to use an image as map or you can use the custom map provider which allows using map tiles offline.
I would also recommend that you visit the following documentation page and example which use the UriImageProvider:
In this blog you can find how to provide offline server with tiles stored in IIS directory.
the Telerik team