Moreton Bay Rail Link - Petrie station still sub-optimal?

Sub-optimal layout for Petrie. 

There have been some recent changes to the plans for Moreton Bay Rail Link (MBRL), most of them sensible, such as an island platform at Kippa-Ring (Redcliffe). Despite a re-design at Petrie, now sensibly incorporating fly-overs, the track and platform layout still appears to be sub-optimal. Petrie is where the MBRL splits off from the existing Caboolture Line. Unfortunately, it appears in the plans that inbound services (to Brisbane) from both lines will share a platform at Petrie.

Typically, where two train lines merge, it is best practice to allocate a separate platform for each train line. Using a separate platform for each line allows for more operating margin and reliability, as trains can wait for their turn on the merged track at the station platform. Instead, Petrie will have a shared platform. The shared platform will result in trains entering the merged track approx. 2.5 mins apart (due to station dwell time), instead of approx. 1 minute apart (on yellow signals) for separate platforms. The shared platform will increase the occurrences of trains waiting outside of the station if the train arrives early, or a train from the other line arrives late.

An optimal design in Barcelona Source: http://carto.metro.free.fr

There will be three tracks south of Kippa-Ring, aided by the Lawnton to Petrie triplication, allowing for express services to overtake all stations services between Petrie and Lawton. Due to the above mentioned constraints, having a shared inbound platform at Petrie will result in limitations for overtaking opportunities - in fact an express train would not be able to catch up with and overtake the all stations train until at least Lawnton, making the Lawnton to Petrie triplication useless in the inbound direction.

Unless the publicly available plans are an incorrectly drawn "artists impression", then the track and platform layout at Petrie requires an urgent rethink. There should be separate platforms (preferably an island platform) for inbound MBRL and Caboolture Line services.

MBRL TMR Webpages:
http://www.tmr.qld.gov.au/moretonbayrail
Carto Metro Free (excellent track maps):
http://carto.metro.free.fr