Assuming that the line to Melton will be quaded, plenty of scope to remove all necessary level crossings at the same time. Would not be a great look to rebuild level crossings from 2 tracks to 4.
The order of the three crossings out in this section is all to do with quadruplication of the section from Sunshine to Robinsons Road Junction.
First by 2023 we do Fitzgerald Road (Road over rail), and Robinsons Rd (road under rail), the you do the quadding and then new station at Deer Park and probably road overpass there. Quoted in media release Derrimut road by 2025.
Exactly how it is to be quadded is still a mystery.
But the road under at RRJ allows for the original rail layout as proposed all at grade.
Most likely RRL track pair on left (South side) with the two main lines peeling away to the the left at RRJ , with teh Down Ballarat track on a single track overpass over Up & Down RRL Tarneit tracks, Up Ballarat tracks connects into Up Traneeit track at grade right at Robinsons Road just before the underpass. Separate sparked Met track pair on the North side of teh existing RRL track pair . Station alterations at both Ardeer and Deer Park no doubt.