Re: 73 speculation. The 73 exists as is for the Fall board period, but, 73 shifts are not a part of the main sign up. Rather, 73 shifts are being signed during what are know as small signups. This allows them to cancel the route at almost anytime rather than having to wait until the Winter signup since those drivers just go onto the spare board.
ETS has been in this position before. I seem to recall the 510x, or maybe it was 73 that did this for one sign up, and certainly there was at least 2 sign ups were the routes that formerly served Millgate and were due to shift to Davies, went on the small sign up since they would need different schedules once the shift was made. Of course, that never happened because the Valley Line never opened and ultimately, ETS just opened Davies to coincide with a new board period.