"I don't see how he could do it without an ok from 'above'."

I don't either. I would put my money on Winfield Scott.

Scott owed Lincoln his loyality because of a congressional inquiry started by Lincoln into why Scott had been relieved as army commander during the Mexican-American war.

Lincoln, Washburne, and Scott were all closely involved in the Whig political party and at one time Scott was considered as a candidate for President along with another Whig Zachery Taylor.

From correspondance between Scott, Washburne and Lincoln, Scott and Lincoln saw eye-to-eye on the question of the disposition of the forts.

Anderson had a connection to both Lincoln and Scott and thereby a possible connection to any plot.

All of this circumvented Buchanan and his efforts to come to some peaceful agreement with South Carolina before Lincoln came into office.

This is another reason why I say that so many of the upper command structure of the United States Army, such as Samuel Cooper, Robert E Lee, Joe Johnston and others resigned their commissions and headed south.