Personally I still think, as I've said elsewhere, that the whole Carlisle jail thing is a product of the imagination of poet and author Andrew Lang. Although I don't know the origins of his poem I am tempted to think he took Lady Scott's version and spun his own story around it. I have looked at a lot of versions of this song/poem and this is the only one I have found which mentions Carlisle!

THE BONNIE BANKS O' LOCH LOMOND
Andrew Lang (1844-1912)

There's an ending o' the dance, and fair Morag's safe in France,
And the Clans they hae paid the lawing,
And the wuddy has her ain, and we twa are left alane,
Free o' Carlisle gaol in the dawing.

So ye'll tak the high road, and I'll tak the laigh road,
An' I'll be in Scotland before ye:
But me and my true love will never meet again,
By the bonnie, bonnie banks o' Loch Lomond.

For my love's heart brake in twa, when she kenned the Cause's fa',
And she sleeps where there's never nane shall waken,
Where the glen lies a' in wrack, wi' the houses toom and black,
And her father's ha's forsaken.

While there's heather on the hill shall my vengeance ne'er be still,
While a bush hides the glint o' a gun, lad;
Wi' the men o' Sergeant Môr shall I work to pay the score,
Till I wither on the wuddy in the sun, lad!

So ye'll tak the high road, and I'll tak the laigh road,
an' I'll be in Scotland before ye:
But me and my true love will never meet again,
By the bonnie, bonnie banks o' Loch Lomond.