If you wanna go with Interrail or Eurail you need a pass that covers Switzerland (Switzerland One Countrypass or GlobalPass) as Tirano is the borderpoint of the Railnetwork :)

Note that Switzerland offer own passes that covers more kinds of Transport + reduced fares for more mountains as Eurail/Interrail. (For example with Ship ride on Lake Lucerne or Lac Leman is for free with the own offers of Switzerland. Or the scenic Postauto “Busrides” along few passes like Palm Express 

Here are some offers for Switzerland only:  SwissRailpass, SBB Dayticket, SBB Saverdayticket or Promotional Offers like these.


For the Centovalli Route Locarno - Domodossola (another scenic Route in Switzerland/Italy) you need a Interrail/Eurail Globalpass or you use one of the Swiss passes  :)

Is the interrail one-country pass Switserland valid for the route Lucarno-Domodossola? I read that this traject is considert as part of the Swiss trainnetwork. (see also the SBB map in the link)  

Yes, whole route, as are also these other passes that Seewulf mentions. It is a Swiss railline where all Swiss tickets are acceoted. As is also (once again) hidden somewhere in the country info-pass benefits.

Actually for my own personal circumstances it became a moot point.

I am not from Europe, and so i can not get an Interrail. And the Eurrail which I can get doesn’t have a Switzerland only pass. 

I do thank you all for the answers, and i looked at all options. For my particular journey I get the best value-convenience ratio from a 4 day “global” pass from Eurrail, mainly because I am going in 1st class. Also it’s 1 single purchase rather than a patchwork of tickets to save 10 Euro. 

@Laurence Smith  maybe you share your Journey details and we find the best solution for you :)

If you are traveling just within Switzerland the SwissFlexiPass (covers almost all kind of public transport in Switzerland) is a option.

@Laurence Smith@Govert Vastenburg 
Here you can find a map where Interrail/Eurail is valid in Switzerland Eurail/Interrail Map Switzerland

@Govert Vastenburg  as you can see on the map the Bernina Bus Tirano - Lugano is covered (Reservation needed and i recommend to book asap as the seats on the bus are limtited) :)
If you select Eurail/Interrail you pay just the reservation fare.

The first class version of that pass (now called Swiss Travel Pass Flex) (504 EUR for 4 days/month) is quite a bit more expensive than the global Eurail pass (328 EUR) so it really depends on the particular itinerary. E.g. if it includes the Jungfraujoch, then maybe the Swiss Travel Pass could come out cheaper since it has 50% reduction instead of just 25%.