One country passes are only valid in that one country, you cannot use them to travel in neighbouring countries.

While there are a handful of exceptions to this rule, that journey is not one of them.

Your options are to use a global pass instead or to pay seperately for the Swiss portion of your journey.

To confirm, the key variable is where the travel ends, not where it begins?

Daft simple: at the border-those stations that once, when there were still those checks by what you call customs and we immigration. Or even more often: the exact geographical point were the border is over the tracks-this is used for fare-calculations as such. INTErnat. fares are simply the sum for the various national parts and these can differ an awful lot. As such that system has been in force and was very widely used for well over 1 century now, but it still amazes those who never thought of it.

I may hence also be where it starts IF your journey would start in Swiss and you go to IT-or from FRance or SLOvenija.

As A-GO is not a place where you will stay forever, you probably will also have to get more tickets to travel onward-so think a little further for that too!

With a One Country Pass Italy you can only travel within Italy, as the name of the pass says. The whole route you use the pass for has to be within Italy.

There are a few exceptions to the rule, like the German Rail Pass, which is valid on a few international routes and the Sweden One Country Pass, which, at least has been, valid to Oslo and Copenhagen. 

No, the key is that it has to start and begin in Italy.

Border stations outside Italy included in the pass:

Chiasso (CH) and Modane (FR). 

To Switzerland the Italy One Country pass works till Domodossola, Chiasso and Tirano.