Looking at their timetable it shows catering as being available as far as Edinburgh.
Ostensibly, yes. So in practice , probably about as far as Berwick.
But I've done a few trips where no catering was provided; it's not really a major selling point, unlike LNER. I even had one where an announcement at Tamworth was saying how refreshments will be "brought to your seat", even though the lack of catering was stated on JourneyCheck several hours prior.
If catering is important to anyone making a long journey on XC then I recommend bringing your own supplies.