Seemingly for the last two seasons the places have gone to the top two placed Highland League teams with a valid SFA club license....allegedly....
From wikithicki....
The 2012–13 Scottish Challenge Cup, known as the Ramsdens Challenge Cup due to sponsorship reasons with Ramsdens, will be the 22nd season of the competition. It will be competed for by 32 clubs, which includes the 30 members of the Scottish Football League, and for the second season running, the top two Highland Football League clubs with a valid SFA club license.
Inverurie Loco Works who finished fourth and Wick Academy eighth of the Highland Football League qualified for the competition for the first time after being asked to compete following their work in the SFA's Club Licensing programme. Clubs ranked higher such as Forres Mechanics are not compliant with the programme so the qualification spot moved to a lower ranked club. Buckie Thistle and Deveronvale were ruled out due to being invited to last season's competition.