I've bought Europa Spezial tickets (E 39.00 each way) from Frankfurt to Lauterbrunnen (Switzerland) and back. The ticket to Lauterbrunnen was online ticket specifying all the train number and time. The ticket back to FRA is a printed ticket from DB sent by regular mail. It doesn't show the train numbers in the Switzerland portion, only the routes (Interlaken Ost / Bern / Basel). For the German segments (Basel / Mannheim / FRA) the train number is specified in the ticket. My question is does anybody know whether in the Switzerland section I'm allowed to avail any train (and/or boat) as long as I stay on the specified route. Thanks advance.
Yes, you are. The SBB fare regulation only specifies routes and days of travel as well as kind of trains (e.g. including ICs or excluding)...
Reservations aren't possible on domestic inter-city trains in Switzerland. So you're free to use any train, and don't need to make any kind of seat reservation for that stretch of you trip in Switzerland.
I'm not sure about an Europa-Spezial-Ticket and segments outside of Germany, but I have used the similar Dauer-Spezial-Tickets inside of Germany. The specified trains on a Dauer-Spezial_Ticket are the express trains of the Bahn (ICE/IC/EC), not the regional trains connecting to them. Even when a regional train is specified on the ticket, that does not mean you have to go on that train, just that that leg is covered. There is a provision, called "vor- und nach-lauf", which says that you can take any regional train after midnight to get to the first express train, and any regional trains up until 10 AM the following day to get to your destination.
As for the Swiss segment, I would imagine you can take any train on that route (boats, ?, I wouldn't be so sure). But check for sure at a ticket counter in Germany before starting.
Thank you all for the response. After returning from my trip I'll update this with what the DB and SBB people says about this matter.
Just got back from my Switzerland/Germany trip using my Europa Spezial ticket. The scheduled time and train number specified in the ticket matters only for German section of the route. Within Switzerland any stop over can be taken on any train at any time as long as the route is maintained on the specified date of the ticket. Also a train journey can be replaced by the BLS boat that goes on the same route by paying the difference between the boat fare and the train fare. This is true for both going to Switzerland and return.