Now DJF this is how it actually is and remember that when you have multiple stopping patterns you will not be able to get 20 trains per hours. With timing of all stops and semi express the most you can get is about 14 trains an hour on the T2 inner west.
Liverpool, City via Bankstown (then Town Hall): Currently 4, New: 0 (-4)
Lidcombe, City via Bankstown (then Town Hall): Currently 4, New: 0 (-4)
Leppington, City via Granville limited stop: Currently 8, New 8 (0)
Homebush and Parramatta all to city Currently 4, New 4 (0)
Liverpool, city via Regents Park: Currently 0, New 2. (+2)
Campbelltown via Sydenham: Currently 4, New 0 (-4)
Campbelltown/Reveseby via Airport: Currently 10, New 14 (+4)
A total of 14 trains an hour each way.
To get 18 to 20 trains around the circle some T2 services are going to have to be diverted on to the suburbans between homebush and strathfield which will then affect T1, T9 and intercity services. There are 14 T1 services and 8 T9 services and I think 8 intercity services.
Some fiddling of the tracks at eveleigh might help this situation but it is getting very tight because of the frequency lost due to multiple stopping patterns in this section of the network.
Based on the new timetable which came into effect last Sunday and measured arriving at Central between 08:00 and 09:00, this is the current situation:-
Liverpool via Bankstown to Town Hall - 4
Liverpool via Bankstown to Museum - 2
Lidcombe via Bankstown to Town Hall - 2
Lidcombe via Bankstown to Museum - 2
Total T3 to City Circle - 10 (6 Town Hall + 4 Museum)
Leppington - 8
Parramatta - 4
Ashfield - 2
Total T2 to City Circle - 14 (Town Hall)
Macarthur/Campbelltown via Sydenham to Museum - 4
Macarthur/Campbelltown via Airport to Museum - 5
Revesby via Airport to Museum - 5
Total T8 to City Circle - 14 (4 via Sydenham + 10 via Airport)
East via Museum - 18
West via Town Hall - 20
The conversion of the Bankstown Line to metro will free up 10 paths on the CC (4 to Museum and 6 to Town Hall) with another 2 spare paths available to Museum.
Under the proposed new operational pattern after the Bankstown Line removal from the Sydney Trains network, the services for T2, T4 and T8 will be as follows:-
4 additional services at key stations, which suggests they will be semi-express and probably the reinstated Liverpool via Regents Park services. That would bring T2 up to 18tph, which seems a bit of a stretch with the mixed stopping pattern, unless they cancel the Ashfield peak hour services bringing it back to 16tph. It would seem more likely as an all stops pattern, but the proposed service pattern is still to be confirmed. There's no prospect of diverting any T2 semi-express services to the Suburban tracks as they are already maxed out at 20tph with T1 and T9 services. 4 T9 services in the peak are already forced to use the Main tracks to Sydney Terminal because of the lack of paths on the Suburban.
2 additional services are proposed from Cronulla to Bondi Junction, 1 from Waterfall and 2 from Hurstville. There will be 4 South Coast Intercity services which will be diverted to Sydney Terminal via the new crossover from the Local to the Main to access the Dive at Erskineville and the 1 Intercity Thirroul service will continue to Bondi Junction, bringing T4 up to 19tph from the current 15tph (excluding the 3 Intercity services to be diverted to Sydney Terminal). Although it hasn't been confirmed, as there will no longer be a Bankstown Line service or T8 via Sydenham, I expect that T4 will become an all stations service from Wolli Creek to Bondi Junction, in addition to the Hurstville to Bondi Junction service.
An 80% increase is proposed on the Airport Line, bringing it up from 10tph to 18tph. 2 additional services are proposed from
Campbelltown and 2 from Revesby. It is obvious that the current 4 peak hour services via Sydenham will be diverted to the Airport Line to achieve 18tph. That means that there will be no suburban services running on the Illawarra Local from Wolli Creek Junction to Central and there will only be the limited number of South Coast Intercity and South Regional services running on this section of track as far as the Illawarra Dive to Sydney Terminal, which seems such a waste when it could be used for additional T8 services to supplement those via the Airport Line.
As grog pointed out, the purported 18tph on the City Circle for T2 via Town Hall, assuming it's feasible, will balance the same frequency on T8 via Museum, which on the face of it makes complete sense. However, I would suggest that this could be an interim measure until the ATP/ATO digital upgrade is completed, which would enable an increase from 40 up to 48tph on the City Circle, allowing for a redistribution of increased services via the flying junctions across the City Circle, including T8 via Sydenham.