I know VXC have VT numbers on Voyager displays, but haven't seen that kind of ID on a journey planner before?
It wa s a Virgin gimmick that (rather like buses) you could turn up at a station and know that the VT99 service at xx15 was via Milltown to Seaside and the VT98 at xx45 went via Leathertown to seaside.
It was designed to be useful at places like BNS where you might have trains from Manchester and Newcastle both bound for Reading or Penzance, if operation princess had allowed the high frequency service, then there could have been 2 such services an hour, so the service number would have been important. on most other long distance franchises there are not that many choices, or that high a frequency service.'
It is similar to the named services, or the named lines on LU, or indeed the 'colour' lines in some places.