Or, more to the point, how do we rationalise the continued existence of the castrums following the loss of the XIV Legion's top leaders? Who or what is keeping the outposts from falling apart from the lack of supplies?
And while we know that one particular tribunus still lives, it's apparent that
he's currently travelling incognito, in an effort to infiltrate the Crystal Tower and steal its secrets.
So I doubt that he's actively giving commands to keep the occupying Imperial forces together. Anyone care to speculate?