I guess the decision was made to use doubled-up 185s before 195s were thought of, but I really think they may be a better option for the semi-fasts.
The Transpennine and Northern franchises commenced on the same date, and the bidding processes ran pretty much concurrently. CAF could have offered First Transpennine the class 195 at around the same time as they did with Northern, if First had any interest in procuring any rather than the class 397s and loco hauled sets that they did do. And why would they, when there's already a ready made fleet of 3-car DMUs specially designed for the route operating over it, with purpose built maintenance facilities in place?
The problem with threads like this is the massive disconnect between speculation and reality.
Whilst the Scarborough facility will be built and optimised for maintaining mk5 stock, there's no reason it can't or won't change in the future.
Indeed: As only a light maintenance depot, I wouldn't have thought that it would have too much equipment specific to the maintenance of class 68 locos and stock, and being seemingly operated by Transpennine Express, rather than CAF, there shouldn't be any problem stabling there whatever future stock the franchisee feels like - Though based on the terms of the franchise agreement, that other CAF product, the class 397, seems the most likely alternative subject to electrification.
The York TPE depot currently maintains 185's, but they will no longer be running through York in a few years' time. I read Northern's new 170 fleet would be maintained there but not sure how accurate that is.
Are Siemens planning on moving out of the depot completely, then? I suppose it would make sense, with none of their fleet passing the site any more - Though it's not a million miles away from the Hull - Manchester route that will still be served by 185s.