It was X’Trapolis set 176M-175M and 174M-173M:

https://vicsig.net/index.php?page=suburban&section=rollingstock&set=175

It was specially modified to reduce the acceleration rate, so that it wouldn’t beat the boom gates at level crossings.

https://www.theage.com.au/national/victoria/safety-fears-lead-to-speed-restrictions-for-xtrapolis-train-on-frankston-line-20141021-1194s2.html

Eventually they modified the crossings to increase the amount of warning time, allowing any unmodified X’Trapolis train to run on the Frankston line.

https://www.theage.com.au/national/victoria/traffic-congestion-to-rise-as-boom-gates-come-down-earlier-on-frankston-line-20150915-gjmvp0.html

Meanwhile mixing X’Trapolis trains with the slower accelerating Comeng trains means that timetabling staff can’t tighten up the running times to match what newer trains are capable of.

Minimising the number of service km that older trains run is one way to get more life out of them, but only in the short term – keep doing it for too long, and you end up with your entire fleet run into the ground!

With X-trap units currently has been stored at Newport sidings for test runs to Werribee in which I hear December 2016 early 2017 is where 10 units be allocated for cross running from Werribee and Frankston (possible growth in numbers).

This means they will be maintained at Newport Workshops oppose from currently at Bayswater and Epping for major works (rumours are part B utilising the jacking road at Newport for the long overdue bogie overhaul project as part of its service life which seen success of the 72 Siemens units, this also secures jobs in Altona as likely Inver Engineering will be external contractor used to do the actual overhauling).

As for the Siemens fleet while operations wise stay the same but will be prodominatly maintained at Westall so otherwords kids no new jobs just staff shuffle.. why Westall you asked?

Well Westall being a small workshop maintains a small group (mainly ex North side or EDI refurb) Comengs while Craigiburn has the rest, the big move means Bayswater depo (now X-trap..less) will end up with a heap of Comeng units simply because the lines in the Eastern burbs meant the Comengs will run less km and thus buying service life (as we recall how long it ended up retiring the Hitachi fleet).