It's been their pitch for two elections now. They would have done a lot of work on the concept. Plus, they campaigned on broken transport promises such as the Ellenbrook line and MAX. As such, they would absolutely be doing everything possible to make sure that as much of it happens as possible.
That is, assuming they want to last more than one term!
Another thing to consider is that the federal Liberal party would be reeling from the MASSIVE smeg kicking handed to them at the state election. That would make them more likely to grant federal funding after the initial resistance - otherwise they would be handed a similar smeg kicking on the federal level, and they know it!
If, however, they can't get everything done, the excesses of the previous state government are in plain sight for anyone that goes to Elizabeth Quay or the Beeliar Wetlands or to where the former golf course was. It's incredibly easy to point at them and say "That's why we couldn't deliver Metronet!"
Because there are tangible monuments to the overspending that can easily be pointed to, the public will be more understanding than when the LNP make the same cry with nothing to point at.