It might not totally rule it out (driving to Germany), if all the teams had a HOO that they had to wait for. We can assume that it sis not snowing when the teams reached the area, but it does seem to me that it hadn't been more than a day before since the roads appear recently snowplowed, and there isn't any "dirty" snow or snow slush in the caps we've seen. The weather on the route might be a factor in whether they were allowed to drive or had to take other transportation to Germany.
I can remember in some past seasons were teams took buses to or from northern Italy. (TAR 3 in Great Britain, TAR 4 in Italy, perhaps?) The main reason I think the speculation has been self-driving is because of the greater presence this season of the Ford vehicles, and this past leg, with the automatic parking system certainly suggests Ford wants to show the features of their new models in the show, and I can see the logic of showing off the GPS system in a country where the teams aren't familiar.