Now, the usage of public transportation is almost inadvisable unless required here in the States (see TAR 16 Leg 1), but in the past two legs - public transportation in St Petersburg would have saved a chunk of money if permitted on all angles...
I have seen racers in the past use public transport as an option (one of them a requirement as a task, TAR 13 Leg 10), but that has been very scarce since TAR 16 Leg 1 - I wonder if the usage of even the Metro was barred during the St Petersburg legs...I would understand if things like the marshrutka would be banned, but I think the normal buses, trolleybuses, trams and Metro should still be permitted if not prohibited by the clue.
...which is sad because the very first task of this past leg took them out to Avtovo Circus, which is very close (about a 5 minute walk) to the world-famous Avtovo metro station.