Constant connection, I'm afraid; they are talking, in a very ambiguous manner, about the current online solo mode; Here are Brookes' comments compiled on a single thread, where this is sadly confirmed.
In my solo online tests it receives about 30 Bytes a second and sends about 8 bytes a second every couple of seconds and then a quick KB burst when opening station screens etc. Hardly optical fibre broadband speeds but yes it is reasonably chatty even if just to keep a connection to the server.