The earliest Scottish Reformed churches had an episcopal polity. Under the influence of Andrew Melville this was briefly dropped, but shortly thereafter it was reinstated. King James was convinced that divine right Presbyterians could secure neither ecclesiastical nor civil peace, and frankly hindsight shows that he was absolutely correct. Thus he returned the Scottish church to the polity of the first Book of Discipline written by Knox.
As part of the reinstating of the bishops (or “supervisors”), James had them ordained by standing English bishops. This was as much an effort to unite the kingdoms of Scotland and England as anything, but as W. B. Patterson notes, it also served to “restore to the Scottish episcopate the historic or apostolic succession that had been lost in Scotland but maintained in the Church of England” (King James VI and I and the Reunion of Christendom pg. 12).
Now of course, a truly Reformed Christian places no faith in manual apostolic succession. He knows that the fullness of the catholic church is present wherever the Word is, but some weaker brothers, presbyter and papist alike, desire apostolic succession. So I suppose they can have it.