Someone, hopefully might know the answer to this. Looking at a loco head on the vacuum brake hose is to by tradition to the left of the draw hook on locos built on lines that were built using that system only. Locos originally built for lines using air brakes only also had them on the same side. However, when vacuum braked locos were additionally fitted with air brakes as well - LNER K2 2-6-0s come to mind here - the vacuum hose was shifted to the right of the draw hook and the air hose fitted to the left. With air braked locos fitted additionally with vacuum brakes - LB&SCR Atlantics for example - the air hose stayed where it was on the left and the vacuum hose placed to the right. So why the shifting of vacuum brake hoses on originally built vacuum brake only built locos?