The amount of time saved would be slightly less than 10 minutes. The amount of time that can be saved between Craigeburn and Seymour is minimal due to the profile of the line and in the worst section of this the train stops 4 times. Even with a Sprinter the only areas fro real 130kph running is beween Craigeburn an Wallan and for a few K's around Kilmore east.
The calculated time savings for 115kph running for the 72 kilometres between Seymour and Shep come to just under 5 minutes, for 130kph running a further 4 minutes would be saved.
So for a service 130kph max line speed to Seymour and 115 to Shep say save 10 minutes for 130kph all the way save 14 minutes.
I believe the reason the Seymour was not included in the RFR project was the expense of trying to straighten out the line between Wallan and Schoolhouse lane would have been way way way more than anyone could possibly justify.
A lack of an upgrade to the Shepparton line is NOT an excuse to not provide immediate improvements to the service and the timetable. The weekend timetable is appalling with only 2 return trains each way and an additional train/bus combination on Sundays. Without any additional rolling stock and faster speeds, three return trains at weekends can be created by adding midday departures from both Shepparton and Southern Cross, instead of trains idling for long periods of time at either end. And by utilising the current Seymour timetable, connecting express coaches between Seymour and Shepparton can fill in the gaps provided by the through trains, thus providing Shepparton with a service every 2 or 3 hours.
Likewise on weekdays, four return train services services can easily be achieved by extending the 1631 Seymour SSH set to Shepparton (saving 17 minutes on the current train/coach service), and this set then departing Shepparton at 0551 the next morning and then taking the path of the 0656 service from Seymour which urgently needs extra capacity at the moment due to overcrowding on the 3VL set which normally runs this service. This would allow the normal morning service (VN set) from Shepparton to depart an hour later at 0730 with more acceptable times from the connecting coach service from Griffith and Cobram. An earlier departure from SCS in the morning (0815?) would allow three am departures from Shepparton - 0551, 0730 and 1130.
The down service from SCS on weekdays could look something like this:
0815ish Direct train (N set)
1232 or 1252 Direct Train (N set)
1631 Direct Train (SSH set)
1822 Direct Train (VN or FN set)
2145 Train/Coach (Fridays only).
Just one last thing - I have had occasion to travel from Seymour to SCS on several occasions during the last 12 months. I cannot fathom why an Inter-City train needs to stop at Wandong. At the most I have seen only up to 2 people joining this train, but usually it is zero! Wandong seems to be well serviced by local Seymour trains. Is there a reason?