Depends where in Scotland and how much they've had to drink.
On a serious note, words like ken, bairn, breekies, stramash are not that well understood by English people. But it's unlikely a Scot would use them when talking to an Englishman.
That's different with Swiss-German. If a Swiss-German person talks to you in German, then they are not talking in their language.
Bairn is northern English too.
Depends where in Scotland and how much they've had to drink.
On a serious note, words like ken, bairn, breekies, stramash are not that well understood by English people. But it's unlikely a Scot would use them when talking to an Englishman.