Hi PQ,

YOu are correct that www.bahn.de shouws Souillac/Sarlat via bus.

But, you don't have to go from Paris to Sarlat via Souillac.

Train from Libourne is direct.

SCNF clearly marks on its schedules when it is a bus, also, and they do so for going through Souillac. It's listed as "autocar" for that section, rather than Corail, TGV, or some type of train.

and these autocars SNCF, or buses substituted for trains like on the Souillac-Sarlat stretch accept railpasses as if they were trains. There are not many of these type SNCF buses but just a few in places that formerly had rail service, like on the pulled up line Souillac-Sarlat that is now a bike path apparently.

The TGV-Est line promises to have Europe's fastest trains - indeed the world trains on tracks speed record was just smashed in trials on this line.

Though regular trains will not approach the 357 mph (? or close) the test trains went i think due to advances in design these new TGVs will be a tad faster than the usual 186 mph on other TGV lines. Currently Europe's fastest train i believe is the German ICE, on the newly built high-speed line Cologne-Frankfurt Airport.