I don’t think the Fort William would ever go over to 67s, as none of the crews who currently work that leg have ever signed them, I don’t think (when 67s worked the Fort William train they had Scotrail drivers, not GBRf as now). Also, 023 & 027 don’t have RETB equipment and are subject to severe speed restrictions on the West Highland Line. I’d expect to see them on the Inverness and Aberdeen portions, leaving the Fort William for one or two 73s.
As the 67s do not have the right ETS to work with Mk5s nor the Dellner couplers, I imagine they’ll work in tandem with a 73?
I also think the 67s working the Fort William portion in the past had to be specially modified with cast iron brake blocks to avoid overheating/excess wear on the long downhill sections. I don’t think 023 or 027 ever had this modification; the only ones with it were 004, 007, 009 and 011 from memory.