How feasible is it travel from Lugano to ultimately,Tirano by train to Como, ferry to Varenna then a train to Tirano to catch the Bernina Express? This way we get to see Como, Lake Como, Belagio and Varenna and not have to have a reservation for a bus that might well sell out if we don't reserve. We are doing a tour of Switzerland with a flexible time schedule with extra days built in and don't want to make reservations. This is in the month of June 2013.
Don't see any reason why not. There is also fairly frequent bus service from Lugano to Menaggio and you can catch a ferry to Varenna from there. Doesn't seem like a "reservation only" bus.
http://www.menaggio.com/ita/e-lakes/Orari_bus.pdf