I thought this might be more relevant to the Sydney thread and the results of updated journey time figures over similarly-profiled selected sections of lines are as follows:
13 km segment:
Perth-Mosman Park (13.5 km): 11 stops, 21 minutes
Perth-Beckenham (13.8 km): 9 stops, 19 minutes
Perth-East Guildford (14 km): 11 stops, 20 minutes
Central-Homebush (12.7 km): 11 stops, 27 minutes
Sydenham-Bankstown (13.4 km): 9 stops, 25 minutes
(Sydney Metro projected time for 13 km: Sydenham-Bankstown: 9 stops, 21 minutes)
30 km segment:
Perth-Armadale: 35 mins, 12 stops; 39 mins, 17 stops
Sydney Central-Glenfield via East Hills: 43 mins, 11 stops; 49 mins, 17 stops
33 km segment (IC=intercity train):
Perth-Clarkson: 33 mins, 9 stops.
Perth-Kwinana: 28 mins, 6 stops.
Blacktown-Redfern: 41 mins, 7 stops; 47 mins, 13 stops; IC 32 mins, 1 stop.
Cronulla-Redfern: 43 mins, 8 stops.
Central-Hornsby via Strathfield: IC 37 mins, 4 stops.
Central-Macquarie Fields via East Hills: 40 mins, 7 stops.
(Sydney Metro projected time for 33 km: Rouse Hill-Chatswood: 35 mins, 10 stops)
Seaford-Mile End: 48 mins, 21 stops; 43 mins, 13 stops.
Adelaide-Munno Para (diesel): 43 mins, 13 stops.
Ferntree Gully-Parliament: 43 mins, 10 stops.
Southern Cross-Dandenong: 47 mins, 16 stops.
Flinders Street-Werribee: 42 mins, 9 stops.
Brisbane (handicapped by track profiles):
Central-Ebbw Vale: 43 mins, 10 stops.
Central-Loganlea: IC 41 mins, 5 stops.
Central-Wellington Point: 52 mins, 12 stops.
Central-Narangba: IC 41 mins, 6 stops.
47 km segment (IC=intercity train):
Perth-Warnbro: 38 mins, 9 stops
(NSW)Thirroul-Bombo: IC 48-54 mins, 9 stops
(Qld)Beenleigh-Varsity Lakes (49km): IC 32 mins, 5 stops
70 km segment (IC=intercity train):
Perth-Mandurah: 51 mins, 10 stops
Sydney Central-Douglas Park (diesel): IC 63-66 mins, 6 stops
Handicapped by track profiles:
Sydney Central-Thirroul: IC 78 mins, 5 stops
Sydney Central-Woy Woy: IC 72 mins, 4 stops
Sydney Central-Blaxland: IC 67-69 mins, 7 stops
Melbourne (Southern Cross)-North Geelong (diesel): IC 55 mins, 9 stops
The results seem most pertinent to Sydney and region trains, being, by the looks of it, the slowest train services in Australia, allowing for Brisbane's handicap of its inherited track profiles. I've used sections of pretty straight track in the comparisons but have acknowledged that three of the Sydney interurban lines run into profile issues in their outer sections.
You need to take into account the number of intermediate stops together with the distances in making the comparisons. Also, considering many lines have varied stopping patterns, I've used the stopping patterns that have a similar number of stops where possible.
It does seem that of all the Australian systems, only the upcoming Sydney metro line (and Gold Coast line between Beenleigh and Varsity Lakes) are able to challenge or match Perth's journey times. Perth shows what is possible with a conventional suburban rail (and note that it's not only the new lines but the 19th century legacy lines that are run fast as well) and is I reckon a good benchmark for other states to emulate. Any observations or comments on this would be appreciated.