There are times when the Yardmaster has to physically go out in the yard. The location of the trailer makes that easy. The yard crew stays in that trailer as well. The closer the better when the shit hits the fan.
Is the Jamaica Yardmaster being mentioned here also the same person for Jamaica Storage Yard (the diesel yards about 3,000 feet west of the station platforms)? It seems like locating them more in the vicinity of the 'former' JAY tower would make them more equidistant to the three big yards (from a geographical standpoint, at least).
Johnson avenue used to have a yardmaster also. Jamaica was YARD 1, Johnson AVe was YARD 2 and the storage yard was YARD 3. An New york had one on 21 TRACK.